San Francisco Bay is the artificial and flat Treasure Island, site of the 1939 Golden Gate International Exposition. From the Second World War until the 1990s, both islands served as military bases and are now being redeveloped. Isolated in the center of the Bay is Alcatraz, the site of the famous federal penitentiary. The federal prison on Alcatraz Island no longer functions, but the complex is a popular tourist site. Despite its name, Mare Island in the northern part of the bay is a peninsula rather than an island. San Francisco Bay is thought to represent a down-warping of the Earth's crust between
Recreation Yard (Alcatraz) Recreation Yard (Alcatraz) The Recreation Yard was the yard used by inmates of Alcatraz Federal Penitentiary between 1934 and 1963. It is located opposite the Dining Hall south of the end of D-Block on a raised level surrounded by a high wall and fence above it. Guard Tower #3 lay just to the west of the yard. The gun gallery was situated in the yard, mounted on one of the dining hall's exterior walls. The recreation yard faced the mainland. In 1936, the previously dirt-covered yard was paved. The yard was part of the most violent escape attempt from Alcatraz