The plain on which Puerto Lejos is built rises steeply on it's western side. When it finally meets the ocean, it does so as immense, sheer cliffs hundreds of feet high. These cliffs serve as an effective barrier to invasion from the west, and also a convenient location for batteries of cannon that guard the approach.
A tall tower (called the Duke's Tower) has been built on a rock outcropping near the southern edge of the cliffs. This tower is far and away the highest point on the southern part of the island and offers an unparalleled view of the town and all it's approaches. In addition to serving as a lighthouse this tower contains several extremely large and cunningly crafted 200lb cannon that are reportedly able to strike any location in the area.
The remote location of the Duke's Tower also historically led to it being used as prison, especially for important or sensitive prisoners, as a result it has something of a dark reputation and is said to be haunted.