The oldest masonry fort in the continental United States, the Castillo de San Marcos is a large Spanish stone fortress built to protect and defend Spain's claims in the New World. It's a National Monument and, at over 315 years old, it's the oldest structure in St. Augustine.
Located in the heart of downtown St. Augustine, Lightner Museum occupies the historic Alcazar Hotel, a Gilded Age resort hotel built in 1888 by railroad magnate Henry Flagler. Founded in 1948, the Museum is home to one of the premier collections of 19th-and early 20th-century fine and decorative art in the country. Also a one point, the world's largest indoor swimming pool.
Flagler College, housed in what was once one of Henry Flagler's most opulent Gilded-Age hotels in St. Augustine, The Ponce De Leon Hotel, is now a private four-year college. It is a National Historic Landmark and tours are available to see the beautiful architecture.