Towering walls of ambition, steel, and concrete, dams have generated power, moderated rivers’ flow, and have dramatically altered aquatic ecosystems the world over.

Through the years, National Geographic has covered dams’ complexities: the environmental risks they pose; how they can help and hurt human communities; and what happens when people decide to tear down a dam. Here are some of our favorite recent stories about the megastructures:

After nearly a century of bottling up Washington State’s White Salmon River, explosives disabled the Condit Dam on October 26, 2011, freeing in a flash millions of gallons of water and roughly 700 Olympic swimming pools’ worth of silt. Cameras captured the river’s dramatic liberation in this time-lapse video, which National Geographic first published two