Compare Berlin to Rome by Rail by Geckos Adventures vs Romantic European - Start Amsterdam, End Paris, Classic Group by Insight Vacations

Day 1 Berlin

Guten Tag! Welcome to Berlin! Your adventure begins with a welcome meeting at 6 pm today. Berlin's nocturnal nightclub scene is a class in itself so perhaps go and discover it tonight after the meeting. Don’t stay up too long as tomorrow you’ll have a tick-list to go through if you want to say you have visited Berlin!

Day 2 Berlin / Overnight Train

This morning, perhaps visit Mauerpark, which literally translates to Wall Park as it sits on the former Death Strip of the Berlin Wall. If the weather is nice the atmosphere is truly Berlin. In nearby Kastanienallee's pubs beer is cheaper than water. In the early afternoon, you'll board a train to Szczecin in Poland, where you’ll connect to your overnight train bound for Krakow. Don’t be late!

Day 3 Krakow

Possibly the best-known Polish city, Krakow was the residence of Polish kings from the 11th to the 17th centuries, and its old town is a World Heritage-listed site. Which means you have some exploring to do! Take a stroll around Wawel Castle which sits on top of a hill next to the Vistula River. It provides a magnificent backdrop to Krakow. Rynek Glowny, the town square, dates back to the 13th century, and is surrounded by awesome buildings, with the Cloth Hall as the centrepiece. There will be plenty of time to explore the city, so visit St Mary's Church, shop for amber or crafts, or just walk around with your jaw agape at all the old-world glory of the place. Find out why Mariacki Hejnal (the trumpeter on top of St Mary's Church) sounds like his tune is cut in half. Sample Obwarzanki while doing that. What’s Obwarzanki? Well, you'll find out.

Day 4 Krakow

If you want to tear yourself from the magical Main Square, venture out of town to visit the Wieliczka Salt Mines, a deep underground network of tunnels and chambers that goes some 135 metres below. The Blessed Kinga Chapel is a highlight not to be missed, with all its fancy salt chandeliers and carvings. You might want to take a day trip to learn more about the history of World War II at Auschwitz (Oswiecim) and Birkenau concentration camps and museums, sites where some of the worst atrocities were perpetrated (it's confronting, but important). A visit to Kazimierz, the former Jewish quarter in Krakow, could be a great idea after visiting Oswiecim. Krakow has many cellar restaurants and pubs and a thriving cultural scene too, so head to the streets, dip into some awesome street food and never leave Krakow without trying some Pierogi. Ask locals (or your leader!), they’ll tell you where to go!

Day 5 Prague

Next up, journey to Prague. It's kind of a lengthy trip (approximately 7 hours), so try to nab a window seat and get cosy. This city is a wonderland of architecture, with buildings from the Middle Ages all the way through to the modern avant-garde. They don't call it the 'City of a Hundred Spires' for nothing. Check out the Gehry-designed Dancing Building (also called the Fred and Ginger Building) on the banks of the Vltava. Don't miss Prague Castle, because it's not only the biggest castle in the Czech Republic, but it is oh-so-pretty too. It's where you'll find the famous St Vitus Cathedral and Golden Lane. A walk through the Jewish Quarter is also a must. Hip literary types can visit the resting place of Franz Kafka. Afterwards, why not take a seat in one of Prague's underground bars and sip some absinthe or a Pilsner. Some of the best fun in Prague is had after the sun goes down, when the magic of the Old Town really comes alive.

Day 6 Prague

Another day in Prague and so many possibilities. Discover the Bohemian Prague: extravagant, political, passionate, and fuelled with Czech Water. Learn how the Bohemian artists, writers, dissidents, and their mentality shaped the nation. Don’t forget to sample some of the best Czech beers and traditional and modern Czech snacks along the way. If you feel like going for a day trip out of the city, ask your leader to help you organise a trip to Kutna Hora’s Sedlec Ossuary, or The Church of Bones if you like, a small Roman Catholic chapel that contain the skeletons of between 40.000 and 70.000 people. Back in Prague remember that the nightlife in Prague is some of the best in Central Europe. Whether dance clubs, beer-halls or underground absinthe bars are your thing, there's something for everyone. The city also boasts one of Europe's most respected jazz scenes. If you find yourself out until the early hours in a jazz club, have a wander along Charles Bridge or the Old Town Square as the sun rises for magical photo opportunities.

Day 7 Cesky Krumlov

Depart Prague and travel by train to the southern Bohemian town of Cesky Krumlov (approximately 4 hours). This picturesque medieval town dates back to the 13th century and is straight out of a fairytale. Cesky Krumlov (pronounced 'Chess-key Kroom-love') means 'crooked meadow', which is befitting, since the town is nestled in a sharp bend of the Vltava River. It also comes complete with a castle on a hill towering over the cute little old town, which boasts a collection of beautiful old buildings and a confusion of cobbled alleyways. Check out the castle and its epic Masquerade Hall, or climb the tower for aerial views of the town. If the weather's fine and you have two or three hours up your sleeve, take a relaxing raft or canoe trip on the river that winds right through the centre of Cesky Krumlov. This is a classic summer pastime.

Day 8 Vienna

Today travel on a series of trains to to Vienna, the capital of Austria (approx 5 hours). Once the centre of the Habsburg Empire, Vienna is today a cosmopolitan city with music in the air and the grandeur of a golden past. Art lovers will be delighted by the vast array of museums available including the Albertina, the Leopold, Kunsthalle Wien and the Museum of Modern Art. Those with an interest in 19th and 20th century Austrian art should visit the Belvedere Palace, home to Gustav Klimt's famous painting, 'The Kiss', check out Hundertwasserhaus or discover the Secession Building with its gold laurel-leaf dome. Upon arrival you might like to indulge in a traditional Viennese coffee and Sacher torte, before capping off the evening with a spot of Mozart, Bach or Schubert in a concert hall.

Day 9 Vienna

After a quick overview of what this great city has to offer your leader will take you to the famous Naschmarkt food and produce market, where you will have the option to try all sorts of weird and wonderful things. You will have the rest of the day free to explore Vienna at your own pace. You might like to head out to Schönbrunn for a guided audio tour of the summer palace designed by Empress Maria Theresa herself. Here, the Gloriette Monument boasts killer views of Vienna. The palace gardens are free to all visitors but there is a charge for entrance and tours of the palace. If you feel like watching dancing horses, catch a dressage show at the Spanish Riding School.

Day 10 Budapest

Take a train from Vienna to Budapest (approximately 3 hours) and explore this exotic 'Pearl of the Danube'. Since the collapse of Communism, Budapest has experienced something of a renaissance. Glamourous and glitzy shops and restaurants sit alongside old-world architecture and groomed boulevards. Budapest is the perfect city to enjoy from the water. From here you'll be able to see the magnificent buildings that line the banks of the Danube River and the bridges linking Buda to Pest (who would have thought?). Cross the Chain Bridge for spectacular views of the Parliament Building and the Castle District. Make sure you head down to the river after dark to enjoy the floodlit spectacle. Head out to Statue Park to see all the communist monuments that were removed from the city streets after the fall of the Iron Curtain. One unmissable activity is to soak in the hot thermal baths. There are loads of these around the city centre and they range from classy and elegant to simple outdoor types. Some even have chess boards so you can exercise your brain while rejuvenating your body.

Day 11-12 Budapest

Enjoy two free days in Budapest. Exploring the historical Buda castle is definitely one way to do it! Forget about the bustling city and lose yourself in the history of the castle and palace complex of the Hungarian kings. The winding streets of Castle District dates back to the 13th century. And there is an old, mid-19th century local pastry shop there! Join your leader on a trip to Szimpla Kert, one of Budapest's famous ruin bars. They originated as squats hidden in inconspicuous side streets, and have since become an inherent part of Budapest's night life.

Day 13 Lake Balaton

Catch the train this morning through Hungary’s green countryside, past manicured vineyards, fields of lavender and woodlands to Lake Balaton. This sprawling freshwater lake is surrounded by ancient fortresses, underwater caves and historic little villages calling out for exploration. Perhaps grab an ice cream and take a stroll through Tihany Town, the oldest medieval village in the region, or pop on a swimsuit and explore the incredible underground lake caves. The water here is so pure you can actually see the bottom! If you’d prefer time out in the sun instead, there is always the portion to simply relax by the lake shore.

Day 14 Zagreb

Another train, another country. Catch an afternoon train to Croatia's capital, Zagreb. On arrival take an orientation walk on which your leader will point out local amenities and attractions you might want to visit along the way, such as a number of excellent museums to visit including the quirky Museum of Broken Relationships. Ask any questions you might have about the city during the walk.

Day 15 Zagreb

Today is a free day in Zagreb, so check out both the upper town and the lower town to understand the city's culture. The tallest building in town is the gothic Zagreb Cathedral, with iconic twin spires that dominate the city's skyline. Ban Jelacic Square is the city's central point, which is surrounded by multiple structures that reflect different periods of Zagreb's past. There is so much to see and do here, the hard thing is deciding what to choose.

Day 16 Lake Bled

Travel by train to the lakeside town of Bled. An eye-popping spot, Lake Bled is found at the edge of the Julian Alps in Slovenia. Needless to say, there are lots of outdoor activities on offer to get the blood pumping. Upon arrival why not head out by bike around the lake or to Vintgar Gorge (4km) and walk through the natural canyon? Explore Bled Castle, perched atop the 100-metre cliff overlooking the lake, or catch a pletna (small wooden boat) over to the island in the middle of the lake to ring the wishing bell. Take a day trip to Lake Bohinj, situated within a glaciated valley in the Julian Alps. There, you can ascend Mt Vogel by cable car for awesome views of the ranges. If the weather is clear you might even see Triglav, the highest peak in Slovenia. For a sample of Bled cuisine, look no further than the famous Bled Cake – a vanilla, custard, cream and pastry delight.

Day 17 Lake Bled

No better place to get active than on a full free day in Bled. Go for a lake walk (or run if you feel like!) in the morning, or do your hot yoga poses on the grassy bank of the lake. You won’t find a better set up for it than in Bled! Afterwards perhaps enjoy a full day adventure around the Triglav Massive, including some white water rafting and other blood pumping activities! Check with your leader for all the options and book in advance not to miss out. If you don’t feel like going crazy, just enjoy the beauty of the place; perhaps find a quiet spot near the lake and spend a day reading your book.

Day 18 Venice

Board the train and brace yourself for some amazing scenery on the way to Venice (approximately 5.5 hours). Venice is one of a kind, built over a hundred small islands connected by 400 bridges. As well as all those romantic canals, it has all the hallmarks of a fine old Italian city: world-class food, performance, art and architecture. Use your free time to explore – the best way to go is on foot. Take in all the famous sights, like the Grand Canal, the old-world shops of the Rialto Bridge, the Palace of the Doge (ruler of Venice), the Piazza San Marco and its golden basilica, and the Bridge of Sighs. Don't even think about leaving until you've eaten some tiramisu. This is where the dish was born, and they know how to do it.

Day 19-20 Venice

There are shops, markets, galleries, churches and stunning buildings around every corner - don't miss the opportunity to take a gondola trip through the romantic canals! Don't even think about leaving until you've eaten some tiramisu. This is where the dish was born, and they know how to do it. Fancy a tipple? Prosecco is the drink of choice here; match it with a pasta fazool and embrace your inner Dean Martin. Now, ‘that’s amore.’ As this is a combination trip, your leader and the composition of your group may change in Venice. There will be a group meeting to discuss the next stage of your itinerary. You're welcome to attend, as this is a great chance to meet your new fellow travellers.

Day 21 La Spezia

Travel on a series of trains (approximately 5 hours) to the Liguria region. La Spezia, a medieval port town whose name is derived from its historic importance in the spice trade, will be your base for exploring the truly epic stretch of coast known as the Cinque Terre (approximately 30 minutes' train ride away). In La Spezia appreciate indulging in the foods of the Liguria region, which take advantage of the products of the Mediterranean. Pesto is a speciality, and is often served with pasta, green beans and potato. Focaccia is also a speciality, and makes a tasty start to lunch – team it up with some cheese and ham and you have a simple yet delicious picnic.

Day 22 Cinque Terre

Cinque Terre’s colourful houses built into cliff faces are an amazing feat of engineering. Those Italians aren't afraid of nothin'. Hike along the famous paths between the villages. Olive groves and vineyards cover the mountains that plunge into the sea, so brace yourself for some crazy, crazy views. You can walk as many sections as you like, or jump on a train between any of the villages or get back to base in La Spezia whenever you want. Notes: Due to recent landslides in the area it is currently not possible to walk the Via dell'Amore and the coastal section between Manarola and Corniglia. There are alternative inland routes, however these are of a higher physical rating and involve steep ups and downs. It is possible to take the train or a bus for these sections. Due to safety reasons some sections of any path can be closed at short notice.

Day 23 Florence

Board a train bound for Florence (approximately 3.5 hours). You'll arrive around mid-afternoon. Get a feel for the heart of Tuscany – birthplace of the renaissance, capital of Tuscany and cultural hub of dear Italia. It's brimming with religious monuments and Renaissance masterpieces. No wonder a third of Europe's fat-cat artists lived here back in the day! The minds and talents of the Medicis, Leonardo da Vinci, Raphael, Brunelleschi, Machiavelli, Donatello and Michelangelo all flourished here. Join your leader on a visit to the Mercato Centrale (the central market). Your leader will teach you some words in Italian, and then it's off to the various produce stalls for you to try your new language skills.

Day 24 Florence

It's best to see the main sights of the 'outdoor museum' on foot – the Pitti Palace, the Ponte Vecchio, the Arno River front, the many statues and monuments of the Piazza della Signoria, the Palazzo Vecchio, the 13th-century Duomo, Baptistry and Belltower and the Santa Croce Church. It's a dizzying list, but don't forget to visit the Uffizi, one of the world's oldest art galleries and a work of art in itself. And of course there's Michelangelo's super-famous statue of David in the Galleria dell'Accademia. What a guy.

Day 25-26 Rome

Head to Rome by train (approximately 2 hours). Time for some Roman around. Arrive in Italy's capital and dive head-first into all it has to offer. Crowded with ancient ruins and religious monuments, Rome still pulses to the beat of modern life and is packed with designer shops, restaurants, cafes and exciting nightlife. Don't miss the Colosseum, Arch of Constantine and the Forum (the centre of ancient Rome). And no visit would be complete without a trip to Vatican City and St Peter's Basilica. Entry to the Basilica is free, and there's a small charge to climb the dome so you can catch the awesome views from up there. The Vatican Museum and Sistine Chapel are also well worth your time before. On the last day it's time to say ciao to your new travel companions, and you're free to depart whenevs. Notes: The Vatican Museum is closed on some days, including most Sundays. On the last Sunday of the month, it's open and free (but expect large crowds). Check the Vatican website for these dates: www.vatican.va. Tickets for the Vatican Museum can be booked online at http://biglietteriamusei.vatican.va/musei/tickets/do. The Galleria Borghese can also be booked online at http://www.galleriaborghese.it/borghese/en/einfo.htm. The best day for your visit to the Vatican Museum will be the morning of departure day.

Day 1: Arrive Amsterdam

Welcome to Amsterdam, enjoy a day of leisure. Join your Travel Director at 17:00 for a Welcome Reception. Mingle and get to know your fellow travellers as you cruise along some of the many quaint, tree-lined canals, to explore the heart of the Old City, before enjoying a pleasant evening of dinner and wine at a local restaurant.

Grand Hotel Amrâth Amsterdam.

Dinner with Wine

Day 2: Rhine Valley to Würzburg

Relax with a scenic drive along the Rhine Valley to Würzburg. See the mighty Marienburg Fortress – the immense baroque palace of the Prince Bishops and one of the most important landmarks in Germany. On arrival, visit the imposing Würzburg Residenz, a UNESCO World Heritage Site, with a Local Expert. Marvel at intricate decorations and lavish staterooms.

Maritim Hotel Würzburg.

Breakfast, Dinner with Wine

Day 3: Rothenburg and Golden Prague

In the morning, venture to Rothenburg ob der Tauber, the most well-preserved town on the Romantic Road. Continue East to the Czech border, passing the town of Pilsen renowned for its beer, to reach the Golden City of Prague. In the evening, perhaps take a river cruise through the heart of the city?

Hotel Royal Prague.

Breakfast

Day 4: Prague, City of a Hundred Spires

Explore Prague with Insight Choice. Choose to walk the courtyards of the Castle and visit the imposing St. Vitus Cathedral. Alternatively, join your Local Expert through the Jewish Quarter and hear about the history, traditions and legends of the Jewish people and taste Trdelník, a traditional Czech pastry. Then, the city is all yours to explore. Perhaps rummage through the renowned antique stores or shop for the finest Bohemian crystal? In the evening, why not enjoy an Optional Experience in the Czech countryside?

Hotel Royal Prague.

Breakfast

Day 5: Through Bohemia to Budapest

Start the day with a journey through the beautiful forested countryside of Bohemia. Journey to Hungary, following the River Danube to Budapest.In the evening, join a Local Expert to enjoy a scenic dinner cruise, whilst looking out over beautiful city views. Budapest boasts one of the most spectacular night time vistas, earning it the nickname 'Pearl of the Danube’.

Hilton Garden Inn, Budapest.

Breakfast, Dinner with Wine

Day 6: The flavours of Budapest

Your orientation takes your along the grand Andrassy Avenue to Heroe's Square. Stroll through the alleys of the Old Town of Buda and admire sweeping views from the Fisherman’s Bastion with a Local Expert.Stand atop Gellért Hill where the colossal Liberty Statue stands in front of the Citadella watching over the city. Marvel at extensive panoramic views as you look out over the famous river dividing Buda and Pest - the two sides linked by the mighty Chain Bridge and the elegant, newer Elizabeth Bridge. Continue your travels, past the Turul Monument, a large eagle statue overlooking the town of Tatabanya, to the Austrian border and through pleasant farming country to the imperial capital of Vienna.

Hilton Vienna Park.

Breakfast

Day 7: Vienna and the Habsburgs

In the morning, there is the option to join a private tour of Maria Theresa's Schönbrunn Palace and formal gardens. Get your camera ready for a drive around the famous Ring Road. This grand boulevard, built along the lines of the old city walls, showcases many of the capital's architectural masterpieces, including the Opera House, magnificent Hofburg Imperial Residence and Parliament building. Later, join your Local Expert for a walk through Innere Stadt, the first district and historic core of Vienna. Sit down for traditional coffee and cake and mingle with locals at a cosy café.​

Hilton Vienna Park.

Breakfast

Day 8: Lake Wörthersee to Venice

This day's route takes you past quiet villages, through Styria's forested mountains and into the Carinthian Lake District. Continue past Europe's warmest lake, the Wörthersee, to cross into Italy near Tarvisio. Then follow mountain valleys and cascading streams down to the Veneto Plain en route to the unique city of Venice. Arrive by private boat to your hotel. In the late afternoon and early evening, sip a cocktail at Caffè Florian, whilst you are serenaded by an ensemble of talented musicians. Afterwards, stroll past the Doges Palace and the famous 'Bridge of Sighs' to Principessa restaurant for a magical dinner. Indulge in traditional Venetian dishes that are enriched with inspiration from seasonal produce, before returning to your hotel.

Eurostars Residenza Cannaregio, Venice.

Breakfast, Dinner with Wine

Day 9: The Magic of 'La Serenissima' Relaxed Start

In the morning, prepare to embrace this most romantic city. See the immense Campanile and Doge's Palace on St. Mark's Square, connected to the ancient prisons by the Bridge of Sighs. Join a MAKE TRAVEL MATTER® Experience as you witness the skill of glassblowers on a visit to a traditional arts centre. The rest of the day is at leisure. Perhaps shop in the small arcades or why not cruise the Venetian lagoon to the island of Burano for a meal of local specialties and wine?

Eurostars Residenza Cannaregio, Venice.

Breakfast

Day 10: Villa Machiavelli and Rome

Head into the Apennine Mountains and the peaceful landscapes of Tuscany. Meet your Local Host for a guided tour through the house of the Italian Renaissance diplomat and writer, Nicolo Machiavelli, with an included special opening of his private office where he wrote 'The Prince'. Visit the Italian garden with views of the Florence Cathedral and the historic cellar, which has a secret underground tunnel connecting the cellars to the oldest restaurant in Italy. Savour a tasting of wines made from the vineyards surrounding the home, accompanied by delicious samples of local Tuscan fare. Your journey continues as you follow the course of the Tiber to your hotel in the Eternal City of Rome.

Veneto Palace Hotel, Rome.

Breakfast, Lunch with Wine

Day 11: Papal and Imperial Rome

With your Local Expert, visit the Vatican Museums. Insight provides special priority entry to avoid the crowds and gives you behind-the-scenes access to the Bramante Staircase, normally off-limits to the public. Inside the Sistine Chapel, admire Michelangelo's famous ceiling. Continue inside the cavernous St. Peter's Basilica, mother church of the Catholic faith, to see another Michelangelo masterpiece, the Pietà, as well as the splendid dome. Leave Vatican City to cross the Tiber and stand outside the Colosseum, imagining yourself back in the days of the gladiators. The afternoon is at leisure.

Veneto Palace Hotel, Rome.

Breakfast

Day 12: Umbria and onto Florence Relaxed Start

Meet chef Lorenzo at his family farm in Umbria. Explore the art of Italian cooking during an entertaining pasta demonstration and delicious Highlight Lunch accompanied by Orvieto Classico wine. Continue on to your hotel in Florence.

Hotel Adler Cavalieri, Florence.

Breakfast, Lunch with Wine

Day 13: Renaissance Florence

Begin the morning by joining a Local Expert in Florence to view the multi-coloured marble cathedral, bell tower and baptistery adorned by Ghiberti's Gates of Paradise. You also visit the open-air gallery of Renaissance masterpieces in Piazza della Signoria, the political heart of the city. See the area around Santa Croce Basilica, famous for the quality of its luxury goods. In the afternoon, enjoy free time to explore the Renaissance capital. Perhaps take the opportunity to visit Pisa and see the famous Leaning Tower?

Hotel Adler Cavalieri, Florence.

Breakfast

Day 14: Across the Alps to Lucerne

Head north towards the Italian Lake District via Lake Lugano. Continue into the heart of the Swiss Alps, passing through the Saint Gotthard Tunnel, one of the longest road tunnels in the world, before travelling alongside towering mountains and past rushing torrents, down to scenic Lake Lucerne. Upon return in Lucerne, see the town's proud Lion Monument, carved into a limestone cliff and dedicated to the heroic Swiss Guards who died defending King Louis XVI during the French Revolution. Then, take some time to stroll across the covered Chapel Bridge and see the baroque Jesuit Church.

Hotel Astoria, Lucerne.

Breakfast

Day 15: Lucerne and Mt. Stanserhorn

In the morning, embark on a scenic journey by funicular railway and open-top cable car to the summit of the stunning Mount Stanserhorn. Breathe in the pristine mountain air and, on a clear day, witness views as far as Alsace and the Black Forest in Germany. Explore Mount Stanserhorn with Insight Choice. Choose to walk along beautiful scenic pathways for a chance to see marmots and other native animals. Alternatively, join a MAKE TRAVEL MATTER® Experience and hear a conservation talk by a Swiss ranger, to learn about local wildlife and flora. With the day free, there is plenty of time for shopping for delectable chocolate in the traffic-free Old Town. Perhaps venture into the countryside for a delightful horse-drawn carriage ride and meet the local farmers? At night, you are offered a fine selection of restaurants to choose from for your Dine-Around Evening.

Hotel Astoria, Lucerne.

Breakfast, Dinner with Wine

Day 16: Sights and delights of Paris

Journey through the rural French country side of Alsace and Burgundy regions, famous for its vineyards and wines, to arrive in the vibrant City of Light. During your time in Paris, see the impressive Eiffel Tower, the magnificent Notre Dame Cathedral and the imposing facades of the Louvre. Discover the banks of the Seine with its many romantic bridges, see the obelisk in the centre of the Place de la Concorde and drive along the Champs Élysées to the Arc de Triomphe. With the evening free, there are countless opportunities to enjoy the lively atmosphere of this glittering city. Why not visit one of the world-famous cabaret shows?

Le Méridien Etoile, Paris.

Breakfast

Day 17: The food and flavours of Paris

Your exploration of Paris today starts with an Insight Choice. Choose to shop in quaint boutiques like a true Parisian for fashion, perfume or cosmetics with your Local Expert. Alternatively, join an avid foodie as you head into areas where Parisians go about their daily lives to explore small shops and sample local treats and delicacies.  In the evening, indulge in refined French cuisine during your Celebration Dinner at the iconic restaurant La Coupole, frequently visited by the French entertainer Josephine Baker.

Le Méridien Etoile, Paris.

Breakfast, Dinner with Wine

Day 18: Au Revoir Paris

Bid farewell to your travelling companions as your journey comes to an end. Transfers arrive at Charles de Gaulle Airport at 08:00 and 11:00.

Breakfast