Budapest, Hungary—Sweltering Budapest is about to get a whole lot hotter when the week-long Sziget festival, one of Europe's largest outdoor music bonanzas, kicks off on Monday evening, featuring more than 500 concerts by top international acts.

Set on an island of the Danube river in the heart of the Hungarian capital, the 22-year-old festival is one of the biggest in Europe.

Last year's edition drew a record 415,000 visitors from 87 countries.

British pop boasts a stellar presence this summer, with huge names like Alt-J, Florence and the Machine, Elie Goulding, Foals, Kasabian, as well as Robbie Williams, who will open the festival.

Other big acts set to rock the 50-odd stages include Kings of Leon, Avicii, Limp Bizkit, Interpol, Infected Mushroom, The Maccabees, Hollywood Undead, Goran Bregovic, Enter Shikari and Erotic Market.

The festival will also showcase emerging talents such as sizzling French art collective Fauve or award-winning reggae outfit Wailing Trees.

Launched in 1993, Sziget also features circus shows, sports competitions and movie screenings, among other activities.