Blackbeard's Castle or Tower is a colonial stone watchtower originally built by the Danish during their occupation of the Virgin Islands. Called St. Thomas Skytsborg Tower, it was built in 1679 by Danish governor Jørgen Iversen Dyppel to observe the port of Charlotte Amalie and protect nearby Fort Christian from attacks. Due to the fort being on sea level, this tower was necessary to observe incoming fleets before they arrived.
It is not known when this tower started being called Blackbeard's Tower but it could have very well been used by him or other members of the Flying Gang. Nearby on Bellamy Cay the island hosted the notorious Samuel Bellamy and his crew for his brief history of piracy in the Americas.
Despite renovations to the city over the centuries this structure was never touched, possibly due to its reputation. In 1994 the tower was added to the United States' National Historic Landmarks and is one of five in the region. It is still visible today and is a popular tourist attraction.