At the entrance of Lake Izabal stands a stone citadel. Built in the mid-1600s by the Spanish, the imposing structure thwarted thieving pirates from attacking the lake, which was used as a storage facility for transport goods. El Castillo de San Felipe later served as a prison. There are cannons and weapons along with sweeping natural vistas. The site is also home to myriad wildlife, including a variety of monkeys.