The London Mithraeum is a 3rd-century Roman temple to Mithras, discovered during postwar building work at Walbrook and later returned close to its original site beneath the Bloomberg building. The presentation is modern and atmospheric, with low light, sound, and surviving stonework used to suggest the secretive rituals that once took place here.
It is a small site, but a strong one: few places in the City make Roman London feel this close.