They say we don’t know why this royal estate was abandoned. Smallpox might have decimated its occupants before the Spanish had a chance to. They say it had been lost, even though the locals knew where it was. History becomes myth when conquerors refuse responsibility.
The lost history of Troy would be more nuanced than the city depicted in the epics of Homer and Virgil. It’s not entirely clear that the city of legend was on the hill of Hisarlik, whose citidel had been rebuilt nine times before it was finally abandoned by the end of the Bronze Age. The events and characters of the epics were likely determined more by the story teller than by history.
Once you realize the great span of history it’s easier to imagine cities lost in it. It’s easier to imagine a city of gold when your have only gold on your mind. The germ of the myth was apparently a legendary chief of the Muisca people whose ritual offerings of gold and emeralds were thrown into Lake Guatavita. Walter Raleigh, his son Watt, and others wasted their time and lives searching for a city that did exist.
Petra and the Nabatean kingdom were cursed. Roman annexation and new trade routes starved this once wealthy city until the sands buried it. If you can camp there in a carved rock mausoleum and make no sound for forty-one days and nights a hidden door will open to rooms of gold and jewels.
The novelist James Hilton made up this utopia which encouraged explorers to go look for it and various places in Tibet and China to claim they were the Shangri-La.
Plato’s allegory on the hubris of nations abandoned by the gods and submerged in the Atlantic became a popular theme for writers of fictional utopias and pseudoscientific dreamers and deceivers. The claims that Atlantis is the New World and that the ancient Toltecs were the Atlanteans are infused with pernicious racial prejudices.