INmusic is Croatia's biggest international open-air music festival, held annually in late June on the Isle of Youth in the middle of Lake Jarun in Zagreb. Running since 2006, it draws international headliners across rock, electronic and world music.
INmusic takes place over several days each summer on Lake Jarun's Isle of Youth, with multiple genre-specific stages and an on-site campsite for festival-goers.
For the current lineup, exact dates and ticket information, check the official INmusic website linked above.