A massive stone monolith that could be Mexico's most important Aztec relic to be found in decades has been shown to the public for the first time.
BBC News, Mexico City
Roughly the dimensions of an average living room and two metres thick, the slab has lain undiscovered in the centre of Mexico City for 500 years.
Local archaeologist Enrique Alcala says it is a find of world importance.
It is estimated to date from 1501 - just 20 years before the Aztec empire was destroyed by the Spanish.
Mexico City was built on the foundations of Tenochtitlan, the Aztec capital, and the huge sandstone block was a sacred place at the heart of the Aztec empire.
Archaeologists unveiled it in a press conference on Friday.
Many working here simply cannot believe their find.
"We cannot explain what we feel at the moment just to find something. This is very, very, very special," said Enrique Alcala.
The vast block was discovered by accident during foundation work for a new building that was going to be built over it.
The massive stone monolith could have been an altar for human sacrifice, experts say.