Mexico City is sinking because the area was a lake before the arrival of the Spanish. When the Aztecs arrived to their promised land, they found a very large lake called Lake “Texcoco”. But the area was not at all virgin, it was well inhabited by other people. On arrival, the Aztecs were assigned a small island in the west of the lake to stay. It was called “Chapultepec” which means grasshoppers hill. The Aztecs started their live on this island in the middle of the lake, building more artificial islands, the so called “Chinampas”. When the Spanish arrived, they found the Aztec capital Tenochtitlán with impressive buildings, surrounded by broad channels floated with water. Hernan Cortez sent a letter home, saying it was the most beautiful place he ever saw. When the Spanish destroyed the city, they filled the channels with the debris of the destroyed buildings. They cut down the surrounding woods to build ships, and brought lots of cattle to grass, therefore reducing the natural vegetation furthermore. Mexico City was built over the ruins of the ancient Aztec capital in lake Texcoco. The ground is not stable in the former lake, and the destruction of the natural environment led to erosion and frequent flooding. That is why the city is slowly sinking since 500 years.