London's newest cultural destination lies in an unexpected place: beneath the new European headquarters of the financial services and news company Bloomberg.

The London Mithraeum, a temple made by the cult of Mithras that dates back to Roman times, was discovered on the site in the 1950s, but its remains were moved to make way for new construction. Now, Bloomberg has installed a new recreation on the original site, and it's opening to the public on November 14.

The three-story London Mithraeum Bloomberg SPACE brings visitors back to the ancient Roman settlement Londinium using lights, haze, and sound. Created by the New York–based design firm Local Projects, it's designed to make you feel like you're descending through time, until you reach the ruins at what was once ground level, almost 23 feet below modern London's streets, where the exhibition recreates what researchers think the rituals of the cult might have looked and sounded like 2000 years ago.

An artist's conception of what the temple would have looked like in Roman timesJudith Dobie © MOLA

"People walk into the Mithraeum, and it's dark and a bit cold and super quiet, and then as the ritual builds, the entire temple builds around you, almost like standing inside a three-dimensional hologram," Jake Barton, the founder of Local Projects, tells Mental Floss. "It's such a magical experience, to see architecture appear and disappear around you. It never ceases to shock and excite our visitors."

Local Projects worked for years with consulting curator Nancy Rosen Incorporated, artistic consultant Matthew Schreiber, and exhibition architects from Studio Joseph to figure out how to combine the story of the cult, the plentiful ancient artifacts found on the site, the modern castings that represent the objects the temple would have contained, and the ruins themselves, which have been reconstructed using the original building materials (with some help from supplemental stone).

At street level, Bloomberg SPACE displays 600 of the 14,000 artifacts found on the site. James Newton
An interactive exhibit on the Mithraeum mezzanine with a resin replica of a bust of MithrasJames Newton
Dynamic wallpaper features Mithras slaying a bull, the central icon of the cult.

The challenge was to showcase the historical aspects of the site without just showing off a big pile of rocks, illuminating the religious activities and human stories that make it interesting in the first place. "The hard thing in all museums is, how do you make it real, tangible and human?" Barton says. Their solution was to dedicate the upper floors of the Mithraeum to historical context, then leave the lower level to be its own experience.

Six hundred of the 14,000 ancient artifacts of the site are on display on the ground floor, and once you descend underground, a mezzanine features interactive exhibits where you can hear from experts and learn about the beliefs of the cult of Mithras and the rituals performed in the temple. The lower level, where the ruins of the temple are located, is left spare in order to evoke the reality of those cult activities.

The reconstructed templeJames Newton

The temple was recreated based on architectural drawings and photographs from the original excavation and close examinations of the building remnants. The museum uses lighting effects and dramatic music not unlike what you would have experienced if you were part of those rituals 2000 years ago, they say. "We want visitors to have a direct, uninterpreted encounter with this past," Barton explains.

The museum opens November 14 and is free, although reservations are encouraged.