United Islands

There are plenty of music festivals in Prague throughout the year, but United Islands is one of the few large-scale (partially) open air summertime festivals that is completely free! A huge variety of musical styles are represented over several stages from rock to jazz to club music. There's a large focus on local music talent but many artists have been invited from across the world as well such as English electronic duo Audio Bullys. Full details for the festival at the official site, linked below.