At 57,600 m2, the Zócalo is one of the largest squares in the world and where the Aztecs founded their capital city of Tenochtitlan. In the present day, it continues as a gathering place for ceremonies, festivals and parades at the center of Mexico City. Officially known as Plaza de la Constitucion, highlights include the Metropolitan Cathedral and the Palacio Nacional, the seat of the Federal Government. Once Moctezuma's imperial residence, the Palacio Nacional now houses Diego Rivera murals and other artifacts from Mexican history. Nearby is the Templo Mayor - the great Aztec temple, known not only for its architecture but as a bloody historical site of ceremonial human sacrifice at the top of its steep pyramid steps.