If Koffinpuisto (Sinebrychoff's park) is the hipster park, then this is the hippie park. Plenty of things happen here in the summer time, especially those that involve music and sausages.
Don't worry about the people whirling and waving frantically around each other, they're just practising their contact impro moves, and that guy in the women's swimming costume, he's just expressing himself... you should try it.
Bring your frisby if you want to pretend you're not staring.
Mon-Su: Open 24 hours