If you know your Mesoamerican history, then you know that Mexico City sits on what used to be the Aztec empire, literally the ancient capital location. With the modern city now sinking rapidly, it gives new meaning to the term, Montezuma's Revenge. The problem is not really a surprise, it's more that the sinking took as long as it did. The ancient world was famous for its engineering science building a floating city on a lake. Colonial construction and then modern construction replaced all of that with heavy weighted materials. With a constant drainage of groundwater, the land is compressing and dropping lower and lower in level.