For centuries, people have built mind-blowing structures underground. This new series explores the incredible places and spaces beneath our feet.

Underground Worlds reveals the hidden stories of some of the world's most extraordinary underground structures, both natural and man-made, brought to life with spectacular visuals and expert investigation and explanation.

We are taken on a journey across the world, and beneath it, to see just what man and Mother Nature have created out of sight. We visit the largest and most spectacular cave networks ever discovered, gain access to vast operational subterranean complexes, explore forgotten man-made tunnels and venture into mothballed military bunkers.

Each episode features three underground worlds and unpacks each unique story - its conception, its construction, its uses and, in many cases, its repurposing for different future uses.