Vondelpark
I´ll add to Ana´s comment about my experience. I went with my friends to Amsterdam looking for ve knows what and suddenly we found ourselves in this park that we ran into by bike. It was last spring and we couldn´t resist the temptation to lay down on one of the green areas. Also, it was a coincidence that they were celebrating a concert with an incredible atmosphere, we almost couldn´t park the bike. Of course, it´s an obligated visit if you go to Amsterdam, I dare to say that ahead there are various monuments or museums.