© Wikimedia/Hobe/Holger Behr

Rough map of Nan Madol in the Federated States of Micronesia.

The eerie abandoned stone structures are said to have inspired science-fiction writer H. P. Lovecraft to create a similar sunken city that was home to the monster Cthulhu, says Atlas Obscura.

In reality, Nan Madol was once home to the Saudeleur, who ruled the island of Pohnpei for more than a millennium, reported Smithsonian Magazine. The 92 artificial islands of Nan Madol are thought to have been constructed over the course of several centuries, and then eventually abandoned after 1,000 years of habitation.

Rufino Mauricio, Pohnpei’s only archaeologist, has dedicated his life to studying and preserving the ruins, which are built of 750,000 tons of black basaltic rock.