Those red towers look natural. The Romans made them

Transcribed from the audio; small errors are possible.

This is Las Medulas, in northern Spain. Those red towers look like nature made them, but people did. The Romans, almost 2,000 years ago, they came here for gold. But there was a problem. The gold wasn't in big shiny lumps. It was tiny specks, hiding all through the hill, like sprinkles in a cake. You can't pick out sprinkles one by one. So the Romans had a wild idea. Take the whole mountain apart. First, they dug tunnels deep inside it, by torchlight, for months, until the mountain was full of holes. Then came the water. They built long channels to bring a flood from far away. And they let it go. A Roman writer named Pliny wrote about it. He said the mountain split apart with a crash. Then the water washed the mud away. But gold is heavy, so the gold stayed behind, and the mud rushed off toward the sea. Pliny wrote it all down in a book, so we still know how they did it. Today, This place is a world heritage site, so it's kept safe for everyone. And those red towers? They're the parts the water could not take.