San Juan, Puerto Rico
This fort is the biggest construction ever created by the Spanish in the New World. Unlike El Morro, which was created to protect from invaders arriving by sea, the Fort of San Cristobal was made to protect from enemies invading by land. Its construction began in 1634 and was finished in 1790. If you are interested in history, wonder around the many ancient walls where 500 years ago soldiers diligently protected the entrance of San Juan. If you are a photography buff, you'll be gla to know that the vistas are impressive. You can see the coast that leads to El Morro on one side and the Condado area on the other.