Omi is dominated by Lake Biwa, Japan's largest lake. Good soil and plenty of water make this an extremely fertile province. It is also known for the Koga-ryu, a school of ninjutsu from the Koka area. With its closeness to Kyoto, the old Imperial capital, Omi was an important location. When the capital moved to Edo, it became host to a series of post stations along the Tokaido road between the two cities.