Why Are There Miles of Tunnels Underground in Downtown Houston?

While in Houston for the Global Poker and Astros Poker Night, Sarah Herring heads out to explore the mystery behind Downtown's 6-7 miles of underground tunnels. The tunnels are climate controlled, contain restaurants, shops, gyms, and more, and connect more than 95 city blocks. Where did they come from? Why are they there? Who is in them? Herring talks to people in the underground system to get the story.

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