lighthouse

A tall structure topped by a powerful light used as a beacon or signal to aid nautical navigation.

A tower or other structure exhibiting a light or lights, for the purpose of indicating the presence of rocks, shoals, or other dangers to navigation, or for the guidance of mariners when approaching or sailing along a coast, entering a harbor, or navigating a river or other body of water.

A tower or other building with a powerful light at top, erected at the entrance of a port, or at some important point on a coast, to serve as a guide to mariners at night; a pharos.

A building, usually a tower, containing a light to warn or guide ships.

a tower with a light that gives warning of shoals to passing ships