Myoshoji Park (妙正寺公園, myoshojikouen) has a pond and a fountain. In this park, you can watch a lot of wild birds. (Don't feed the birds, there are already too many of them.) It is a nice park to bring the kids.
Tourist info:
There are nice fountains. It has a wide play ground and play equipments like swings and slides.
Access:
0. at Tokyo Station
1. use Chuo line (JR) to Ogikubo(24 min.)
2. walk north (15 min.)