Illustrious past
If you lift and soar from the side of the Popocatepetl volcano - down into the greasy smog - you may arrive at the Cibeles fountain, in a chic central district of the city.
In the history of urbanisation there has never existed such a radical transformation
Jorge Legorreta, architect
Ringed by fashionable restaurants, it is a popular place for locals to come to relax.
The architect Jorge Legorreta often comes here for a lunchtime stroll. His greying hair is neatly brushed over his ears.
His thick moustache dances above a lively mouth. Jorge walks past a rusty steel pipe, about half a metre high.
He points at it. "Twenty-five years ago, this drain was level with the ground," he says, "but the whole area has just fallen away from around it."
Jorge's eyes twinkle as he remembers the city's illustrious past.
It was the jewel of the Aztec empire.
The Spanish conquistador, Hernan Cortes, first set eyes on Tenochtitlan, as it was then called in 1519.
One of his band of soldiers wondered whether it was a dream, calling it an "enchanted vision". It was a beautiful, well-planned floating city built in harmony with its surroundings, in the middle of a lake.
But it was not to stay that way for long.
The Spanish soon drained the water away, and started building.
"In the world and in the history of urbanisation," Jorge says, "there has never existed such a radical transformation."