Imperial Palace

This was Edo Castle, the largest fortress in the world when it was finished, and the seat of the Tokugawa shoguns for over 250 years. The emperor moved in after the Meiji Restoration in 1868, when the capital shifted from Kyoto, and his family has been there since.

The main keep is gone. It burned in the Meireki fire of 1657, killing a large share of the city with it, and the shogunate decided that rebuilding a tower was less important than rebuilding Edo. Only the stone base remains, up in the East Gardens, and you can climb it and stand on the footprint.

Those East Gardens are the part you can actually visit, free, most days except Mondays and Fridays. Inside are guardhouses, the enormous cut-stone walls of the inner citadel, a Ninomaru garden laid out in the Edo manner, and a great deal of lawn where the palace buildings used to be. It takes about ninety minutes.

Nijubashi, the bridge everyone photographs, is at the southern outer edge, across a moat from the plaza and its rows of black pines. The inner grounds beyond it can be visited only on a free guided tour, booked in advance through the Imperial Household Agency, or on 2 January and the emperor's birthday, when the gates open and the imperial family appears on a balcony.

The five-kilometre loop around the moat is the most used running course in Tokyo. Convention is anticlockwise. In cherry blossom season the northwestern side at Chidorigafuchi, where you can rent a rowing boat under the trees, is one of the best in the city and correspondingly full.