(covers information from several alternate timelines)
A small lighthouse
A lighthouse was a structure, typically a tower, housing a light source to aid in maritime navigation. They were found on Earth coasts.
One early lighthouse was the Lighthouse of Alexandria, which was considered one of the Seven Wonders of the Ancient World. (VOY: "11:59")
Fort Point included a lighthouse, which could be seen sticking out over the fort as James T. Kirk and Spock passed near it in 1986. Later the duo passed another lighthouse. (Star Trek IV: The Voyage Home)
An image of a lighthouse was one of a set of pictures in Kirk's quarters aboard the USS Enterprise-A. (Star Trek VI: The Undiscovered Country)
Alcatraz had a lighthouse, which in an alternate reality was destroyed when the USS Vengeance fell to the Earth in 2359. (Star Trek Into Darkness)
During a discussion if the Fair Haven holoprogram should feature fog or not, Harry Kim suggested that the dangers of fog could be mitigated by placing a lighthouse in the simulation too. (VOY: "Fair Haven")