On Sundays, the park is turned into a huge open air flea market where artists sell their crafts, people sell their used stuff and a variety of food stalls cater for all the other needs. On all other days (the sunny ones, mind you) the park is crowded until the wee small hours of the morning, with the usual barbecue/drinking/guitar-playing people.
Apart from the flea market, there is outdoor karaoke. Yes - somebody once decided to carry a karaoke machine plus screen and speakers to the arena-like part of the park.
if you are searching for real rarities on the flea market, come early!
Mon-Su: Open 24 hours