Mexico City is sinking because of the amount of water being pumped out from beneath its foundations.
One of the largest and most populous cities in the world, it was once a lush land of lakes. But over the last 500 years the lakes have been drained and the surrounding forests chopped down.
As the city grew in size, the water problem magnified. With no adequate drainage system, today rainwater mixes with sewage and is used for irrigation.
The city is now at serious risk of running out of clean water. An estimated 40% of the city's water is lost through leaky pipes built at the turn of the century.