Another one of St. Thomas's National Historic Landmarks, Fort Christian was completed by Danish settlers in 1680--making it the oldest structure in the U.S. Virgin Islands.It was built originally to protect the colony and island from hostile marauders. Since its completion, it has served a variety of purposes: a jail, a governor's residence, a place of worship, and a police station. The building acted as a museum for many years, but it is currently under renovation. It will eventually be reopened to the public. While it is closed for the time being, Fort Christian is still a popular site for visitors. Its red walls and imposing clock tower make the building perfect for photos.