Honnō-ji is a Nichiren-school Buddhist temple a short walk from the city hall and one of the most historically loaded small temples in Japan. The current buildings, on Teramachi-dōri, are post-war reconstructions; the original temple — a few hundred metres west — was the scene of the Honnō-ji incident on 21 June 1582, when Oda Nobunaga, on the brink of completing the unification of Japan after a century of civil war, was ambushed by his trusted general Akechi Mitsuhide and forced to commit seppuku as his troops fought a losing battle in the surrounding streets.
The temple grounds include a small museum (Hōmotsukan) with relics relating to Nobunaga and the incident — including a sword said to have been his — and a mound commemorating him in the precinct. The visit is brief but compelling, particularly if you know the period. Nearby Teramachi-dōri itself, with its arcades of small specialist shops, is one of the more characterful shopping streets in central Kyoto.