Huge underworld 'city' under London once home to thousands of people

A vast network of caves, extending over 22 miles, is concealed beneath a car park in one of the world's most bustling cities. These caves are not natural formations but were astonishingly carved out by humans over centuries, with origins dating back to the Romans and Saxons around 500AD, and possibly even earlier according to local folklore.

Standing above these caves, just a short 20-minute train ride from London Bridge, you would never suspect what lies beneath your feet, surrounded as you are by suburban London. In its historical past, Chislehurst Caves served as a chalk mine and mushroom farm before the 100ft deep vaults were deemed perfect for those seeking shelter from the destruction above during World War Two, as reported by The Mirror. When the Luftwaffe launched their bombs in an attempt to force Britain into submission, thousands sought refuge in their nearest Underground station - or in Chislehurst.

By the time the bombs started to fall, a massive effort had been made to clean out the caves, install a hospital, electricity, hundreds of beds, multiple canteens and even a cinema, effectively constructing an underground city.

During the Blitz, the caves would open to the public at 7pm each evening, providing sanctuary as night fell. Adults were charged sixpence a week and children thruppence to stay in what was affectionately known as the Chislehurst Hotel.

Occasional visitors had to find any available space, while regulars claimed their own spots, personalising them as much as they could.

During the war, the Caves provided shelter for tens of thousands of Londoners. At least one girl was born in them and, following a suggestion from the midwife, she was named Cavena Wakeman.

The task of managing waste from the nightly influx of thousands proved too much for the installed toilets, leading to guests being asked to bring their own containers for after-dark emergencies.

"Thousands of buckets in the pitch black. Can you imagine the chaos?" remarked one tour guide.

Historical records dating back to the 13th century mention the caves' use for mining lime-burning chalk and flint. The discovery of a prehistoric skeleton in the ceiling suggests the caves date back to 10,000 BC, when they were used as a refuge during the Ice Age.

In the early 20th century, tourism in the area boomed as rumours spread about the caves' ancient history - a theory promoted by William Nichols, vice president of the British Archaeological Association at the time.

Journalist Milo Boyd, who took a guided tour, said: "When I visited, our guide keenly counted everyone in and out of the tunnels, having handed each of us an oil lantern in case we managed to wander off the path."

He added: "Over the years dogs have been taken down to find those lost in the caverns."

During the caves' more recent, post-war era as initially a rock and subsequently rave venue (Pink Floyd, the Rolling Stones and Jimi Hendrix all performed), it was not uncommon for hungover revellers to wake deep in the caves' bowels, having staggered into their depths after one-too-many.

The conduct of party-goers, who would pour onto the residential streets at 3am following a night in the underground, resulted in the closure of Chislehurst Caves as a music hall in the early 80s.

Nevertheless, this didn't entirely stop the excitement. One morning, guides discovered missing wall lamps in the tunnels.

Upon further investigation, they found that a group of teenage dirt bikers had broken in overnight and used the lights to create a track through the darkness.

"It struck me, as I walked deeper and deeper into the network, the warmth of an early September day replaced by a damp chill, that you would have to be an adrenaline fuelled teenager to venture into the caves alone at night," said Milo.

"At one point our guide struck a huge gong, causing a horrifying cacophony to bounce round and round the tunnels, making clear how far the maze sprawled. We moved on to an underground lake where, spooky rumour has it, a strange, perhaps ghoulishly shaped misty vapour has a habit of appearing to lone adventurers."

These caves were not merely a playground for adventurous teens, but also served as a sanctuary for families during the Blitz. The entire network of caves was plunged into darkness at 10pm each night.

However, if you're curious about how children managed their fear, bear in mind that sleep was as precious as any other commodity in London during the Blitz.

Securing a spot in the Chislehurst Caves would have ensured your safety throughout the night. You would be protected from the 30,000 tonnes of explosives that fell on Britain over an eight-month span, finally allowing you to sleep peacefully after numerous nights of fear and uncertainty, wondering if a bomb was about to pierce your roof.

Tickets for the Chislehurst Caves can be bought at the entrance, but due to limited group sizes, it is advised to book ahead online. Tickets are priced at £8 each, with discounts for children and seniors at £6, and under 3s at just 1p.