treasure city

plural treasure cities

1. historyA city containing great riches, especially one that was the object of plunder by conquistadors.

   1 more example

   The next day he returned to camp with the balance of his ingots, and when they were stored on board the cruiser Captain Dufranne said he felt like the commander of an old-time Spanish galleon returning from the treasure cities of the Aztecs. “I don’t know what minute my crew will cut my throat, and take over the ship,” he added.

   1913, Edgar Rice Burroughs, The Return of Tarzan, New York: Ballantine Books, published 1963, page 220

2. biblicalA fortified structure or storehouse where grain, military supplies, precious metals, and other valuable resources were kept.