Miami Beach is a coastal resort city in Miami-Dade County, Florida, United States. The municipality is located on natural and human-made barrier islands between the Atlantic Ocean and Biscayne Bay, the latter of which separates the Beach from the mainland city of Miami. The neighborhood of South Beach, comprising the southernmost 2.5 sq mi (6.5 km2) of Miami Beach, along with Downtown Miami and the PortMiami, collectively form the commercial center of South Florida. In 1979, Miami Beach's Art Deco Historic District was listed on the National Register of Historic Places. The Art Deco District is the largest collection of Art Deco architecture in the world and comprises hundreds of hotels, apartments and other structures erected between 1923 and 1943. Mediterranean, Streamline Moderne and Art Deco are all represented in the District.