Kasai Rinkai Park : enjoy the sea !
Close to the city, yet, it's the seaside
If you want to get away from high-rise building without going too far, Kasai Rinkai parc is your place.
One station before Disneyland (Maihama), on the Keiyo line, it takes you 20 minutes to get there. If you go there, you need to bring your lunch with you because the only restaurant there is a fast food one.
The large parc is very green and features a bird nesting area where no humans are allowed. That side has a kind of wildness that you do not find in other parcs of Tokyo.
There is a nice aquarium to visit too.
What makes Kasai Rinkai parc nice is that it is facing the sea and there is a nice beach to enjoy in spring and summer, and early autumn.
Tokyo Water Bus
From Kasai Rinkai Parc, you can take a boat to go navigate back to Odaiba or Asakusa.
It's a 50 minutes "drive" to Odaiba and you enjoy the Tokyo bay at its best :
Godzilla bridge, inaugurated in 2010, Tokyo port area, Rainbow Bridge, ...
In spring and summer, the wind coming from the sea and the speed of the boat is quite refreshing and a solace from Tokyo extreme heat and humidity.