Built on a muddy island on the lake at the Valley of Mexico in 1325, the Aztec capital of Tenochtitlán was occupied and destroyed by the Spanish forces in 1521 led by Hernán Cortés. The area became the foundation of the modern Mexico City. The site of the Templo Mayor or the Great Temple was discovered in 1978 and has became part of Mexico City’s Historic Center which was designated as a World Heritage Site in 1987.