Tokyo Bay coastal defences. 19th-century map showing ships and coastal defences in Tokyo Bay, Japan (then known as Edo Bay), with the city of Tokyo (then known as Edo) on the coast at lower left. The bay covers an area of around 922 square kilometres. It is connected to the Pacific Ocean by the Uraga Channel (upper right). The peninsulas at the mouth of the bay are Miura Peninsula (lower right) and Boso Peninsula (upper right). Across bottom is a list of soldiers and Samurai warriors defending the bay. This map dates from 1852, and was published in the 1860s. The bay and city were renamed to Tokyo when the city became Japan's capital in 1868.