An ordinary-looking office block has something very surprising underneath it.

Beneath a modern building on Lower Thames Street, London lies a scheduled monument. As you go down the stairs into the basement, you will come across the ruins of a Roman house with a bath house attached to it dating from about the year 190.

Billingsgate Roman House and Baths is the remains of a large private residence discovered in 1848. It is the only private Roman house in London that can be visited – and it has a rich history.

David Harry, a London tour guide, shared a video on TikTok exploring the house. He said: “London is full of shocking surprises. This 1960s/70s office block has an enormous secret in it.”

As he entered the building and went down the stairs, he said: “This is a Roman house dating from about the year 190 and not only is it a Roman house, it has a dark secret in it as well because along here isn’t just a house, it’s got a bath house attached to it.”

Taking his viewers along for the ride, David explored each room, starting with the Roman ‘hot room’ which “would have been so hot that your skin would have been fried off your feet.” Next, he showed viewers the ‘cold room,’ which was used for changing clothes.

Another feature of the ancient Roman house is a tepidarium room, which David said would have been used for business and it “would have been comfortable but very hot.” Billingsgate Roman House & Baths has been preserved for nearly 2,000 years and was declared a scheduled monument under the Ancient Monuments & Archaeological Areas Act 1979 – so any damage caused could be a criminal offence.

In the caption of his video, David wrote: “Discovered in 1848, and preserved at a time when normally ruins were just destroyed, this amazing private house dating back to Roman times contains its own spectacular bathhouse. It’s a mystery why the bath house is here, as it would’ve stood in the way of the view of the River Thames, which was just next to the building.

“The bathhouse was discovered by the Victorians, and then when the rest of the coal exchange was pulled down in the 1960s, the rest of the secret was uncovered. It’s the only private Roman house in London that can be visited, and is an unparalleled archaeological treasure.”

David’s video has racked up a staggering 793,000 views, 34,000 likes and hundreds of comments. TikTok users who saw the clip commented on how amazed they were.

One said: “That’s incredible. Imagine what else is laying beneath us.” Another added: “That is so cool oh my God! What an amazing find” while a third commented: “How amazing. I would love to discover something from the Roman times.”

Several users asked David in the comment section what the ‘dark secret is’. He responded: “It’s more of a mysterious surprise, Roman private houses hardly ever have a bathhouse attached. There’s a theory that it was originally a temple and then a brothel.”

Billingsgate Roman House and Baths is open for the public to visit on Saturdays between April and November. Tickets cost £12 per adult and £10 per child 14 years old or under.