Located near the Bayside Marina, there is a small peninsula jutting out into the bay, with very steep seaside cliffs on all sides. At the peak of the cliff side, there is a small, flat, circular structure which resembles the foundation of a lighthouse.
It has been theorized that there was originally a lighthouse on the peninsula in the beta, but it was removed from the final version of the game for unknown reasons. Players believe that it would have been difficult for game developers to remove the lighthouse's foundation from the terrain, so they just left it there.
Another theory is that this lighthouse is a kind of reference to Alcatraz, a prison also existing in the beta game.
A Skimmer spawns next to the peninsula, which could be a hint to what the structure's purpose was in the game.
In the beta mission The Truth Is Out There, after CJ picks up The Truth in Bayside, an FBI agent stands on top of this structure and successfully downs the player's helicopter. However, it wasn't proven that the mission walkthrough looked like that.
The supposed "Lighthouse" is also believed by fans to be the foundation of an artillery piece, as it has the same appearance, and the location on the western borders of the map are very similar to the United State's artillery positions on their western borders facing the Pacific Ocean. The Cold War is canon within the GTA series, so this could be truthful as GTA San Andreas is only set 1 year after the fall of the Soviet Union, and the United States' defense could still be active at the time.