"Cyclopean and many-columned Y'ha-nthlei" is the only Deep One city named by Lovecraft. The name may have been inspired by the Lord Dunsany character "Yoharneth-Lahai", "the god of little dreams and fancies" who "sendeth little dreams out of PEGANA to please the people of Earth."
In "The Shadow Over Innsmouth", it is described as a great undersea metropolis located below Devil's Reef just off the coast of Massachusetts, near the town of Innsmouth. Its exact age is not known, but one resident is said to have lived there for 80,000 years.
In Lovecraft's story, the U.S. government torpedoed Devil's Reef in 1928 as part of a raid on the town of Innsmouth.
Other authors have invented Deep One cities in other parts of the ocean, including Ahu-Y'hloa near Cornwall and G'll-Hoo, near the volcanic island of Surtsey off the coast of Iceland.
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