Shiba 公園

For 150¥ you can enter this nice park close to hamamatsucho station on
yamanote line. There are all kind of O. Wells style creepy buildings
around it, that make you feel a bit observed. But you should invest a
visit. Doesn't seem to be famous amongst tourist and salary men as
well as old people come here for a hide out. Bringing a picnic or
bento is a superb idea.