Kyoto was a city in Honshu, Japan. Formerly the capital of the nation-state that controlled the region, the city was the birth place of Hoshi Sato. (TOS: "The Cage"; ENT: "In a Mirror, Darkly, Part II")
According to episode writer Mike Sussman, who created the biography of Sato, Kyoto was also where Hoshi was buried following her death on Tarsus IV. The section of the biography containing this information was not seen on screen.
According to the Star Trek: Star Charts (pg. 32), Kyoto was the capital of Asia.