On Saturday night it was in Vienna the "Langenacht der Museen" that means that the museums were open till 01:00!!! There was a meeting point were u had to go and buy your ticket(wich was very cheap 12€ and only 10€ for the students!!!) and catch suttle busses so u can reach all the museums in Vienna. I went there at 20.00 till 00.30 (i couldn´t walk anymore) and i visited Belvedere(it is great, i like Gustav Klimt very very much) , Museum of Natural history, M. of Art history, the architecture museum in MQ, and MuMoK (i don´t recommend this one).
I was surprised when i saw how many museums were on the list....83 WOW and there are more museums in vienna... It was really very nice ... u could see so many people running from the one museum to the other trying to see as much as they can. Further information here.