This description is about the legendary lost continent of Mu. Mu is believed to have been an ancient civilization that existed in the Pacific Ocean thousands of years ago. It is said to have been a large island or continent with a highly advanced culture and technology. Theories about its existence have been around
From Wikipedia
Mu is a lost continent introduced by Augustus Le Plongeon (1825–1908), who identified the "Land of Mu" with Atlantis. The name was subsequently identified with the hypothetical land of Lemuria by James Churchward (1851–1936), who asserted that it was located in the Pacific Ocean before its destruction. The place of Mu in both pseudoscience and fantasy fiction is discussed in detail in Lost Continents by L. Sprague de Camp.