It is the heart of Edo Castle; entry is free and it closes two days out of seven.
Of the castle that stood here, what remains is the base of the keep (天守台, a stone platform you can climb up onto) and the Fujimi turret. The rest is lawn and trees inside the walls and moats, which, by contrast, are all still there: you are walking within the castle perimeter more than inside a garden.
The eastern part of the imperial grounds, on the site of Edo Castle.
ℹ️ Free entry, but gated: closed on Mondays and Fridays, and in the evening.
🚉 Takebashi · 12 min walk
Holidays in Japan? Plan them with us.Over 2,000 real places, a day-by-day itinerary.FreeOpen the map →Sword Art Online
Kirito and Asuna's date in the first episode of ‘Sword Art Online II’, the one that opens the Phantom Bullet arc: they meet in front of the Ōte-mon gate and walk in the park, and the three benches in a row on which they sit are on the open ground of the Honmaru, where the keep of Edo Castle stood. In the anime the scene is set in autumn.
Sources: renote.net · anitabi.jp · seichi-junrei.info · furaba-animeseichi.blog.jp · kunaicho.go.jp
Nearby
National Museum of Modern Art, Tokyo (MOMAT)500 mphoto by Wiiii · CC BY-SA 3.0
Ōtemachi Station — Exit C10600 m
Kandabashi Bridge700 mphoto by Syced · CC0
Kōkyo Gaien, plaza and Nijūbashi Bridge800 mphoto by Chris 73 · CC BY-SA 3.0