When you think of engineering marvels, a sewer system might not be the first thing that comes to mind — but Mexico City is home to one of the largest sewer systems in the world.

Spanning thousands of miles, this vast network includes tunnels, treatment plants, and pumping stations that work together to handle the challenges of a city built on a former lakebed. The system even includes the Emisor Oriente Tunnel, one of the longest wastewater tunnels on the planet. It stretches nearly 40 miles and is designed to prevent flooding during Mexico City’s rainy season.

This engineering powerhouse isn’t just about size; it’s a testament to human ingenuity and the ability to adapt to unique environmental challenges. So next time you flush, think about the incredible systems making it all possible — like the one keeping Mexico City flowing.