In this episode we head down into the top secret bunker built to house the entire US government in the event of a nuclear strike on Washington DC. Above ground it looks like a plush hotel, but below ground, but below ground is a whole secret world.
We head to the mountains of Wales in the UK, to a former slate mine that has been brought back to life. Many old mines remain off limits because of the dangers of being underground, but the new owners here have embraced those dangers.
And we visit the vast plains of the Judean Lowlands in Israel, to the Land of a Thousand Caves. The town here was known as Beit Guvrin, and mentioned several times in the Bible as Maresha. Civilizations have come and gone above ground, by the caves have remained throughout.
