Kii-Oshima-Island、located 1.8km off Kushimoto, is the largest island in Wakayama Prefecture. The island has an area of 9.66 km². It is connected to Kushimoto by the Kushimoto-Big-Bridge, a series of three arch bridges, opened in 1999. Before these bridges were built, the way to the island was only by a Junkousen boat. The Japan-U.S. Friendship Memorial Hall on the island commemorates the visit of the trade vessel Lady Washington in 1791.