Vienna to Prague

By day trip, do you mean round trip. The round trip is about 10-11 hrs. Unless you leave pretty early in the morning, you'll get there and have to turn around and come back. Not very practical.

If you leave Vienna at 05:50 you'll get to Prague at 10:19, otherwise it will be after 12:00. If you leave Prague at 17:19 you'll get back to Vienna at 22:04 (eat on the train). So it's theoretically possible, but I can't imagine actually doing it. I found Prague way too crowded, but I'd still give it more than seven hours. Go here - http://www.bahn.com/i/view/GBR/en/index.shtml - for train schedules. Vienna is Wien and Prague is Praha. There are plenty of less exhausting day trips you can take from Vienna.

I agree; very tough as a day-trip. Prague is 1 of Europe's great cities, and deserves more time. What IS possible (albeit a little tight) as a day trip from Vienna, is Budapest. Of course, Budapest is a great city that deserves more time, IF one has it. But if you are pressed and want to see Budapest's highlites, it can be done. That's what I did. I began that particular trip in Vienna and was making my way west into Germany. Due to firm dates on which I had to be back in NYC, I didn't have much time to divert from my planned itinerrary, but did find myself with an extra day after seeing pretty much all I wanted to see in Vienna. Departed very early AM, arrived in Budapest mid/late AM. My stops there included taking the funicular up to the Fisherman's Bastion (and taking in the amazing views), the Holocaust Memorial Center, walking across the Chain Bridge, The Parliament Building and even getting in some swim and massage time at the famous Gellert Baths right before I went to the train station for the return trip to Vienna. It's about 3 hrs each way. Was it a rushed day?! Yes! But I got in some Budapest highlites and did have great fun doing it. I should point out that this was in mid December where (even for someone like me who LIKES cold weather), it was bone-chilling. But that also added to the experience; was fun to see the local xmas decorations.

The round trip is about 10-11 hrs.
... by train. Anout 3.5 or 4 hours each way by car so r/t is 7 to 8 hours by car. Not quite so long by car, but pretty hard work. Going early in the morning and driving back through the night you could have an afternoon there. Dunno what you'd see though. And if you will drive that late let others know so they can stay off the roads.

Theoretically it is possible but practically it is a bad idea. And even worse to try to do it by car. Traffic around Prague and Vienna is very congested and sometimes even around Brno. To be able to do it faster than train you would need super ideal conditions. As a doable day trip I would recommend Bratislava.

or Brno by train