In Civlization and Civilization II, the Lighthouse is a Wonder of the World that your civilization can build. It enables all ships to move an extra square, and in Civilization II, it ensures that none of a civilization's triremes will sink.
The Lighthouse requires the advance of Map Making to build, as well as 200 resource shields. It expires with the discovery of Magnetism.
As far as Wonders of the World goes, the Lighthouse is not very useful, although in a scenario with lots of water, it can be handy to have.