Time Out says
Last edition of this DJ-lead dance music festival, held by the river in countryside outside Zagreb
Located one and a half hours drive (or one hour 45 minutes by train - the best and easiest option for tourists) to the south-west of Zagreb, River Festival is easily within reach of Croatia's capital and is certainly worth the trip. For the last few years it has been one of the best annual events at which to experience Croatia's homegrown underground electronic music talent. Sadly this will be the final edition, occurring over a 12 hour period from 5pm on Saturday until 5pm on Sunday. The event is held in a secluded and beautiful location at the side of the river Mrežnica. Deep house and underground techno come from what is genuinely the best of Croatia's homegrown DJ talent. Take a tent or, like many, just rest beneath the shade of the trees, choosing between swimming in the river or playing games by day, and raving at night. River Festival is noted for being welcoming and friendly. Almost everyone will speak English and by the time you leave you'll know half of the couple hundred strong crowd, including some of Zagreb's best party people.