Vast centuries-old cave once home to thousands is hidden under London

A vast network of caves, spanning over 22 miles, is concealed beneath a car park in one of the world's busiest cities. These caves are not natural formations but were astonishingly carved out by humans over centuries, dating back to the Romans and Saxons in 500AD (and possibly even further if local legends are to be believed).

Standing above these caves, just a short 20-minute train ride from London Bridge, you'd never guess what lies beneath your feet, with suburban London surrounding you.

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, reports The Mirror. When the Luftwaffe dropped their bombs in an attempt to force Britain into submission, thousands flocked to their nearest Underground station - or to Chislehurst.

READ MORE:Harlow car park to become temporary bus station as work on starts on new £15m transport hub

READ MORE:The ancient Essex palace that Henry VIII gave to his wives that you now can't see

By the time the bombs started falling, a massive effort had been made to clean out the caves, set up a hospital, install electricity, hundreds of beds, multiple canteens and even a cinema, resulting in the construction of an underground city.

During the Blitz, the caves would open to the public at 7pm each evening, providing refuge 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 served as a shelter for tens of thousands of Londoners. A girl was even born within these walls and was named Cavena Wakeman, upon the midwife's suggestion.

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? " commented 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 that 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 increased 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 their more recent use post-war as a rock and rave venue, where the likes of Pink Floyd, the Rolling Stones and Jimi Hendrix performed, it wasn't unusual for party-goers to wake up deep within the caves after having one too many drinks.

The behaviour of these revellers, who would emerge onto residential streets at 3am after a night underground, led to Chislehurst Caves being shut down as a music hall in the early 80s. However, this didn't completely put an end to the fun.

One morning, guides found wall lamps missing from the tunnels. Upon further investigation, they discovered 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" Milo commented.

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

These caves were not just 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.

But, 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 in advance online. Tickets are priced at £8 each, with discounts for children and seniors at £6, and under 3s at just 1p.