Osaki Park (大崎公園), or Peacock Park for those in the know.
The playground area isn't anything too special, but this is a very nice park. It's also a free park! If you want to ride the go carts in another area of the park, there is a small fee. I think it's 300-yen to ride them.
The reason for the name (above). I didn't take time to count them, but there seemed to be thousands of peacocks in the above beautiful enclosure.The flamingo area, complete with a waterfall, is beautiful.