photograph by Oquendo via Flickr
La Fortaleza, PR: La Fortaleza was built by the Spanish in the sixteenth century to guard against attack by French, English, and Dutch pirates. Largely burned by a Dutch force in 1625, it was rebuilt and enlarged within 15 years. It has survived as the residence of the island's Governors for more than 400 years. Along with San Juan National Historic Site, La Fortaleza is listed on UNESCO's World Heritage List