The Imperial Palace East Gardens (皇居東御苑, Kōkyo Higashi Gyoen) are a part of the inner palace area and are open to the public. They are the former site of Edo Castle's innermost circles of defense, the honmaru ("main circle") and ninomaru ("secondary circle"). None of the main buildings remain today, but the moats, walls, entrance gates and several guardhouses still exist.
A wide lawn and the remaining foundation of the former castle tower can be found on top of the hill, where the castle's innermost buildings once stood. The castle tower was completed in 1638 as the tallest castle tower in Japan's history. But only a few years later in 1657, it was destroyed by citywide fires and has not been rebuilt since.
In place of the former buildings in the secondary circle of defense (ninomaru) at the foot of the hill, a nice Japanese style garden has been created.
The Otemon entrance to the East Gardens is a short walk from Otemachi Station on the Chiyoda, Tozai, Marunouchi, Hanzomon and Mita Subway Lines. It can also be reached in a 10-15 minute walk from Tokyo Station.