it's called "Jazz Boat" and it's a jazz bar (pretty pub maybe) on the left bank of the Vltava river, nearest tram stop is Arbesovo namesti. it's really very beautiful and stylish, and the biggest advantage is that they close at 4 a.m. -- so if one decided to take a long night out, that is where you go, lol. and the music is grand. never offensive... sometimes bluesy, sometimes more rythmical and vivid. recommend! :)