With its expanse of buildings and concrete, Mexico City may not look squishy—but it is. Ever since the Spanish conquistadors drained Lake Texcoco to make way for more urbanization, the land has been gradually compacting under the weight. It’s a phenomenon known as subsidence, and the result is grim: Mexico City is sinking up to 20 inches a year, unleashing havoc on its infrastructure.

That includes the city’s Metro system, the second-largest in North America after New York City’s. Now, satellites have allowed scientists to meticulously measure the rate of sinking across Mexico City, mapping where subsidence has the potential to damage railways. “When you’re here in the city, you get used to buildings being tilted a little,” says Darío Solano‐Rojas, a remote-sensing scientist at the National Autonomous University of Mexico. “You can feel how the rails are wobbly. Riding the Metro in Mexico City feels weird. […]