Bratislava old town can be walked in about 30 minutes (including stopping to look at the curious Gestapo-style public art).

Honestly, the best thing about Bratislava is that the train trip to Vienna is really cheap. Oh ok, and the hot chocolate is good (and really cheap). Otherwise, it just doesn't compare to other beautiful European capitals. As for Vienna? Sigh - my third visit and it's still one of my favourite cities in the world.

 Eat:

Chocolate chocolate chocolate! My pick of the twin cities:

• Schokocafe Maximilian Delikateso -  The best 20 metres in Bratislava is the area around the main square, which is surrounded by adorable cafes serving chocolate and pastries. I picked this one because of the glorious wall to ceiling chocolate counter and the gilded Art Nouveau interior. The hot chocolate was rich and thick and came to a grand total of 50k (US$2)

• Sacher Confiserie - every time I go to Vienna I make a pilgrimage to the home of the best chocolate cake in the world. Unfortunately,  the Bratislavian train timetable was against me so I couldn't sit down to enjoy my cake with the view of the Opera House. So I took home a piccolo Sacher Torte, housed with its own wooden case.
• Altmann & Kuhne - no-nonsense women preside over the most delightful chocolate shop in town - all the tiny handmade chocolates are packaged in specially designed boxes with tiny pull-out drawers.
• Confiserie Lipizzaner - The Spanish riding school is not just famous for horses, but is also home of the original Lipizzaner cake, an almond chocolate cake with white chocolate icing.
• Cafe Demel - the tiers of chocolate at this famous shop were so overwhelming (all packaged in beautifully decorated boxes) that I couldn't decide and bought nothing. My peek at the cafe area made me want to curl up in the corner with a book. Apparently there's even a chocolate and marzipan museum!

Non-chocolate food items can be found at Naschmarkt, where the locals shop for their gourmet food and pack out the yummy food stalls.

Also try the traditional Viennese breakfast at Cafe Leopold in MuseumsQuartier, which is a modern take on the classic Viennese coffeehouse. If you sit in the elevated glassed-in terrace you can enjoy your bread, cheese, cured meats and coffee with a view of the MuseumsQuartier courtyard.

To Do:

Vienna has lovely palaces, gardens and squares (especially around the Ringstrasse), but I think it's a perfect indoors city - there are so many beautiful museums and art galleries to explore.

• Haus der Musik - a fascinating modern museum about music and the  perception of sounds, as well as the expected musician and orchestra biographies. You can compose your own waltz by throwing dice and conduct the Blue Danube with the Vienna Philharmonic (I was admonished by one of the violinists in German - I think because my timing was too erratic). They have a grand piano in the atrium which anyone can play, and when I was there the sounds of Beethoven's Pathetique second movement drifted up the stairs.
• Wiener Staatsoper - my very first proper opera, and in one of the great opera houses of the world. I was impressed that the Viennese really dress up - tuxes, long gowns, furs. This contrasted with the daggy tourists sitting in the rafters (like me). Although from my seat I could only see half the stage (ticket was only 10 euros!), my personal computer screen translated the Italian lyrics of Il Puritano (who knew there were people called Elvira and Alfonso participating in the English Civil War) so I could sit back and enjoy the singing.

• MuseumsQuartier - a large complex of museums, cafes and outdoors areas for Viennese to sun themselves on a weekend. With limited time, I only visited MUMOK (Museum moderner Kunst Stiftung Ludwig Wien), a fantastic glass and concrete space housing Austria's largest modern art collection, which contains a large collection of Pop Art and disturbing photographs of faeces.

 JetsettingJoyce's Transport tips:

• The Twin City Liner, which goes along the Danube to Vienna, is 17 euro one way and not worth the extra time or expense. Except for a couple of spots along the river and the last 10 minutes when you said into central Vienna, it's not that exciting or scenic. Take the train instead.
• It is much cheaper to buy a return train ticket Bratislava - Vienna (8.30 euro) than a one way train ticket Vienna - Bratislava (14 euro).