Daiba Park might not be the most spectacular of green spaces, but it offers one of the best views of Odaiba from its slopes. It is one of the remaining island fortresses, and you can still see the artillery emplacements (the cannons can be found at Yasukuni Shrine).
Location
Daiba Park, 1 Chome-10 Daiba, Minato, Tokyo 135-0091« Google Maps »
Getting there
10-minute walk from Odaiba-Kaihinkoen Station on the Yurikamome Line