carcosa

A deteriorating Civil War fortress in Louisiana called Fort Macomb was turned into the Yellow King's Carcosa for the season one finale of HBO's True Detective.

During the war the site guarded the Chef Menteur Pass, a water route connecting the Gulf of Mexico to Lake Pontchartrain. It was decommissioned in 1871 and is currently closed to the public.

From wiki:
Carcosa is a fictional city in the Ambrose Bierce short story "An Inhabitant of Carcosa" (1891).

Its name may be derived from the medieval city of Carcassonne in southern France, whose Latin name was "Carcaso".