Temple of Mithras

The London Mithraeum, also known as the Temple of Mithras, Walbrook, is a Roman Mithraeum that was discovered in Walbrook, a street in the City of London, during a building's construction in 1954. The entire site was relocated to permit continued construction and this temple of the mystery god Mithras became perhaps the most famous 20th-century Roman discovery in London.

Source: Wikipedia