of Mexico being characterized by great clumps of seagrass. The area where the two bodies merge between Key West and Cuba is called the Straits of Florida. The warmest ocean waters anywhere on the United States mainland are found in the Florida Keys in winter, with sea surface temperatures averaging in the range in December through February. Duval Street is the main street in Key West and is in length in its 14-block-long crossing from the Gulf of Mexico to the Straits of Florida and the Atlantic Ocean. Key West is closer to Havana (about by air or sea) than it is to Miami ( by air or by road). Key West is the usual endpoint for marathon swims from Cuba, including Diana Nyad's 2013 record-setting swim as the first completed without a shark cage or fins and Susie Maroney's 1997 swim from within a shark cage. Notable places Old Town The earliest Key West neighborhoods, on the western part of the island, are broadly known as Old Town. The Key West Historic District includes the major tourist destinations of the island, including Mallory Square, Duval Street, the Truman Annex and Fort Zachary Taylor. Old Town is where the classic bungalows and guest mansions are found. Bahama Village, southwest of Whitehead Street, features houses, churches, and sites related to its Afro-Bahamian history. The Meadows, lying northeast of the White Street Gallery District, is exclusively residential. Generally, the structures date from 1886 to 1912. The basic features that distinguish the local architecture include wood-frame construction of one- to two-and-a-half-story structures set on foundation piers about above the ground. Exterior characteristics of the buildings are peaked metal roofs, horizontal wood siding, gingerbread trim, pastel shades of paint, side-hinged louvered shutters, covered porches (or balconies, galleries, or verandas) along the fronts of the structures, and wood lattice screens covering the area elevated by the piers. Some antebellum structures survive, including the Oldest (or Cussans-Watlington) House (1829–1836) and the John Huling Geiger House (1846–1849), now preserved as the Audubon House and Tropical Gardens. Fortifications such as Fort Zachary Taylor, the East Martello Tower, and the West Martello Tower, helped ensure that Key West would remain in Union control throughout the Civil War. Another landmark built by the federal government is the Key West Lighthouse, now a museum. Two of the most notable buildings in Old Town, occupied by prominent twentieth-century residents, are the Ernest