A lighthouse is a tower near the coast, equipped with a bright light and a fog horn. The light turns, sweeping the horizon. Each lighthouse has its own unique turning speed, so that narrow beams of light pass across the horizon, and by counting the beams and their colours navigators know which lighthouse they are near. Lighthouse patterns are marked on maritime maps.

Lighthouses mark dangerous cliffs and rocky coastlines, offshore hazards such as shoals and reefs, as well as safe entries to harbours.

A lighthouse was one of the seven wonders of the ancient world. It had a brazier on top. The Lighthouse of Alexandria, Egypt, (the Pharos of Alexandria) was built by the Ptolemaic Kingdom between 280 and 247 BC. It was between 393 and 450ft tall. It was one of the tallest man-made structures in the world for many centuries. It collapsed due to an earthquake after standing for a thousand years.

One of the most famous lighthouses is the Eddystone Lighthouse off the coast of Britain. It is built on a shoal of rock on which many ships had been wrecked. The pictures show what it first looked like (when made of wood) and the stone version by 1890.

There is less need for lighthouses today because of modern means of navigation, such as GPS and radar.