Few buildings on earth have had quite so many owners.

The National Palace in Mexico City stands on the site of the Aztec Emperor Moctezuma's palace, which Hernán Cortés demolished after the conquest and replaced with his own. That became the Viceroy's palace, which became, after independence in 1821, the seat of government.

On its central balcony, behind golden railings, hangs a bell. Not the original from the church in Dolores, where the priest Miguel Hidalgo rang it at dawn on September 16, 1810, calling a crowd to rebellion against Spain. But since 1896, it has stood here so that on the night of September 15, the president can ring it and shout "¡Viva México!" to a packed Zócalo below.

VoiceMap's self-guided audio tours place the palace at the centre of Mexico's long argument with itself, tracing three civilisations through one address: Aztec emperor, Spanish viceroy, and independent republic.