The Imperial Palace Moat which surrounds the castle. The Sakurada Moat is the longest moat in Edo castle. The road surrounding the moat is a popular jogging route.
There are some great parks in the palace park area. The actual palace is closed to visitors except for twice a year but the East Garden is open and is a nice place to stroll around on a nice day.
Tokyo Palace. Unfortunately I was too late, the grounds close around 5.00. Still it was nice to walk along the moat.