|R'lyeh by Decepticoin on deviantART|
Here's how Lovecraft describes it:
The nightmare corpse-city of R'lyeh...was built in measureless eons behind history by the vast, loathsome shapes that seeped down from the stars. There lay great Cthulhu and his hordes, hidden in green slimy vaults.Norwegian sailor Gustaf Johansen, the narrator of one of the tales in the short story, describes the accidental discovery of the city as a coastline of mingled mud, ooze, and weedy Cyclopean masonry which can be nothing less than the tangible substance of earth's supreme terror--the nightmare corpse-city of R'lyeh... loathsomely redolent of spheres and dimensions apart from ours.
TL;DR: An island rose out of the sea, and I instantly thought of Cthulhu. It's eerie how fiction can sometimes show up in one form or another in real life. Crazy, right?