The Lighthouse cannot attack, but it has a decent amount of HP and usually gives players enough warning of an enemy approach to prepare their defenses. Additionally, units can garrison inside a Lighthouse for protection.
The Pharos Lighthouse at Alexandria, Egypt, was one of the seven wonders of the ancient world and remarkable for its architecture and size. It warned mariners at night of shoal waters along the tricky coast. It was actually built by Greek rulers of Egypt who had gained control of the country after the death of Alexander and the breakup of his brief empire. The list of seven wonders was made by a Greek and heavily favored Greek artifacts. Most had relatively short lives, including the lighthouse, which was felled by an earthquake.