A small, uninhabited island just south of the Richmond Bridge, Red Rock Island sits at the boundaries of San Francisco, Marin, and Contra Costa counties. Pyramid shaped and bright red, the island is approximately 5.8 acres in size. In the 1980's developers tried and failed to build a 10 story casino on Red Rock Island. As of mid-2010 the island was for sale with an asking price of $22 million.