Guantanamo Bay NS – is located on 45 square miles (120 km2) of land and water at Guantánamo Bay, Cuba, which the United States leased for use as a coaling and naval station in the Cuban-American Treaty of 1903. The base is on the shore of Guantánamo Bay at the southeastern end of Cuba. The base is on the shore of Guantánamo Bay at the southeastern end of Cuba. It is the oldest overseas U.S. Naval Base, and the only U.S. military installation in a country with whom the United States has no diplomatic relations.