The Hoover Dam is one of the most impressive works of engineering in human history. While it may not quite measure up to the pyramids or the other wonders in pop cultural prowess, it marks a major period of history in American infrastructure.
Constructed at the prime of the Great Depression, this monolithic dam took 6.6 million tons of concrete to construct. If you’re reading this, you probably have a good idea of what the Hoover Dam looks like, but do you know what’s behind those gray walls? Popular YouTube channel “What’s Inside” got exclusive access to see inside the dam thanks to the U.S. Department of Interior. Take a look at the impressive engineering below!