Bratislava, the capital of Slovakia is an easy and fun day trip from Vienna. You can drive there in less than an hour (remember to buy your Slovakian vignette when you pass the border) or take the 1-hour train ride (15 Euros per person; includes public transport in Bratislava; the train station is about a 15-minute walk from downtown or a 5-minute bus ride).
In the historic center of the city, wander around beautiful buildings, explore cathedrals and churches, visit the market and square (definitely stop by the lovely chocolate café right on the main square), or visit the Bratislava castle overlooking the city.
For more information:
- Wikipedia site on Bratislava
- Vienna-Bratislava train schedule and information
- Vienna-Bratislava boat tours