I'm in the London borough of Bromley, and beneath my feet is something that's often described as a cave system.
But it's not actually a cave at all.
It's 22 miles of underground tunnels that at one point became home to around 15,000 people, night after night for years.
So how did these caves get here in the first place?
What was life like in this underground city?
And could we all move back in if things go south?
Right turn.
Straight up.
I'm glad you know where you're going.
So you see how you get the condensation?
