London Mithraeum

The stairs lead you down, away from the traffic of Queen Victoria Street. With each level the city noise grows fainter. The air feels cooler, and the light drops to a low glow. By the time you reach the bottom, you are standing roughly at the ground level of Roman London. The modern city sits several storeys above your head. Down here the floor is dark and the walls are low. Something very old waits in the gloom ahead.

This is the London Mithraeum, the remains of a Roman temple to the god Mithras. It was built in the third century, when London was called Londinium and was one of the largest towns in the province of Britannia. The temple stood on the bank of a small river called the Walbrook. That stream still flows under this part of the City, hidden in culverts. You will not see it, but its course shaped everything here.

So who was Mithras? He was the god of a Roman mystery religion. A mystery religion kept its rituals secret, open only to initiates. The god's name came from Persia, but the cult that worshipped him developed within the Roman Empire. Its central image showed Mithras killing a sacred bull. Followers met in small, dark rooms built to look like caves. That is why this temple sits low and has no windows. Darkness was part of the design.

The membership was exclusive. As far as historians can tell, only men could join. Many were soldiers, merchants and officials... people who moved around the empire. Initiates rose through seven grades, each with its own name and symbols. They gathered for shared meals on benches along the side aisles. Picture a few dozen men, lit by lamps, eating together in near silence. The cult offered belonging, rank and secrets. In a busy port town far from Rome, that mattered.

Now look at the shape of the ruins. The temple is long and narrow, with a central nave and two side aisles. Rows of columns once divided them. At the far end is a rounded apse, a curved recess where the main sculpture of the god would have stood. The walls are built from rough stone with bands of flat Roman tile. This mix of materials was common in Roman Britain. You can trace the whole floor plan from where you stand.

Here is the first surprise. For centuries nobody knew this temple existed. Then came the Second World War. Bombing in the Blitz destroyed much of this area. In 1954, workers were clearing the ground for a new office block when archaeologists, led by William Grimes, uncovered the walls. Then, in the final days of the dig, they found a carved marble head of Mithras himself, wearing his soft pointed cap. The news spread quickly.

What happened next is remarkable. Londoners came in enormous numbers to see the ruins. Tens of thousands queued along the surrounding streets over just a few days. Newspapers covered the story closely. Questions were even raised in Parliament about saving the site. Remember, this was a city still recovering from war. Many streets were still marked by bomb damage. A Roman god rising from the rubble caught the public imagination in a way few digs ever have.

But the rescue was not perfect. The temple could not stay in place, because the office building had to go ahead. So the stones were taken apart and rebuilt on a nearby site, at street level, in the early 1960s. The result was not accurate. Modern materials were added, the layout was simplified, and the temple sat in the open air, far from its true depth. For decades, office workers walked past it without a second glance.

That changed when the media company Bloomberg built its European headquarters on this site. As part of the project, the temple was dismantled again and moved back close to its original position. Archaeologists studied the 1950s records to rebuild it more faithfully. Today it sits in a dedicated space beneath the building, at its Roman depth. It opened to the public in 2017. So the walls in front of you have now been moved twice.

The second surprise came from the mud. Before the new building went up, archaeologists excavated the whole site. The wet ground of the Walbrook valley had preserved materials that usually rot away... leather, wood and other organic remains. Among the finds were hundreds of wooden writing tablets. One carries the earliest known written reference to London. Another is the oldest dated handwritten document found in Britain, from the first century. Look for some of them on display upstairs.

Those finds fill the large glass wall on the ground floor. Hundreds of objects are arranged there, from shoes and lamps to coins, pottery and tools. Each one belonged to someone who lived here nearly two thousand years ago. Take a moment before or after the temple to look closely. These small things tell you more about daily life in Londinium than any grand monument could. They show a town full of traders, writers and craftspeople.

The temple itself has a later twist. Archaeologists found sculptures of other gods here too, including Serapis, an Egyptian god, and a marble group showing Bacchus, the god of wine. Some experts believe the building was later used for other worship, perhaps when the Mithras cult faded. Christianity was spreading through the empire at this time. The original sculptures from the 1954 dig went into the collection of the Museum of London rather than staying on this spot.

Before you climb back up, stand still for a minute. The installation uses light and sound to suggest the temple as it once was. Haze and lines of light show where walls and columns stood. Listen for the low murmur of voices, in Latin and other languages. Then look down at the real stones beneath the projections. Somewhere close by, the Walbrook still runs in the dark. And above you, the City carries on, unaware of the god below its feet.