A Stitch in Haste

"As part of his final assault on Tenochtitlan in 1521, Cortes ordered the breaching of the dike to flood the Aztec city. The water level was not high enough at that point to cause the damage he'd hoped for, but in the long run Cortes may have been more successful than he had planned. The Spaniards, not understanding the complexities of the ecosystem, left the dike in ruins when they rebuilt the city, and as a result saw their new colonial capital flooded repeatedly over the next few centuries."
--Moon Handbooks' "Mexico City"

The more things change...

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To this day, Mexico City is sinking into the lake upon which it was built. This has at least two quite remarkable implications:

1. Heavier structures sink more rapidly, with the result that even on the city's flat streets, the sidewalks have become almost sinusoidal, as larger building take their part of the sidewalk down with them as they sink.

2. Archeological sites can actually be above ground. If, say, a 17th Century building was constructed on the site on an ancient Aztec ruin, and then a 19th Century building is raised next to it, then when the 21st Century rolls around and the 17th Century building is demolished, the Aztec ruins underneath can actually be above the more modern buildings. This occurred right next door to the Constitutional Palace, where the remains of a small pyramid were discovered (and a museum is now located).