It's really hard to say, but one of the recent ones is Kalasataman Vapaakaupunki (Free City of Kalasatama). There anyone can arrange an event free of charge, as long as it is open for everyone. It's a space where anyone can come, where you can chill out, work, play, take part in events and workshops or make your own event. In the first phase Vapaakaupunki was built outside next to a upcoming mall, which has also funded the project.
After that the project continued in the form of Olohuone, Living Room, inside the mall in an empty retail space. The space hosts events almost everyday, and has become a popular place to work. On Saturday evenings there are also DJ- and live music gigs.