The nucleus of the Aztec Empire was the Valley of Mexico, where their capital Tenochtitlan was built upon raised islets in Lake Texcoco. After the 1521 conquest of Tenochtitlan by Spanish forces and their allies which brought about the effective end of Aztec dominion, the Spanish founded the new settlement of Mexico City on the site of the now-ruined Aztec capital. The capital of the modern-day nation of Mexico, the greater metropolitan area of Mexico City now covers much of the Valley of Mexico and the now-drained Lake of Texcoco