Sziget in Budapest (Hungary) looks decent.
I went Interrailing this summer. If you have any questions just ask me!
I visited (in order - places in bold were my favourite);
Helsinki, Finland
Stockholm, Sweden
Bergen, Norway
Copenhagen, Denmark
Berlin, Germany
Prague, Czech Republic
Budapest, Hungary
Ljubljana, Slovenia
Venice, Italy
Munich, Germany
Utrecht, The Netherlands
Amsterdam, The Netherlands
Lille, France
[video="youtube;TJFS7BaO1jc"]https://www.youtube.com/watch?v=TJFS7BaO1jc[/video]