A funicular railway, right in the middle of town, which is a nice retreat when you've tired of all the tourists in the old town or by the castle. You'll find it in the area of Mala Strana and you can get to it most easily via the Legii Bridge.
The funicular leads to Petrin Hill and is 500 meters long. You can get off half way up, where you'll find a nice restaurant with a view over the city. But the best views are seen from the top, from Prague's answer to the Eiffel Tower, even if it is only a tenth the size of the original. Don't miss the hall of mirrors either. You'll have an interesting experience as well as getting a fantastic painting of a battle, done in perspective. It depicts how Jews and students stopped the Swedish army's advance over the Charles Bridge during the final part of the 30 year war in 1648. The Swedes succeeded in taking the castle, on the left bank of the Vltava (Moldau) river, and looting many treasures. But the defenders weren't going to let any enemy over the bridge and in doing so, saved the rich, eastern part of the town from being looted and burnt.
You won't be robbed if you buy your Czech Korunas from FOREX Bank before you leave. The bureaux de change in Prague are not to be messed with!