The Sopot Lighthouse is a navigation facility on the Polish Baltic coast, located in Sopot.[1] It was built in 1903–04 as a part of the Balneological Institute. The extent of its focal length of light has since been reduced to 7 nautical miles (13 km; 8 mi),[2] which, according to existing criteria, no longer formally makes it a lighthouse, although it is still called so. It is open to visitors.[3]