The name of the Mithraeum of the Seven Gates refers to the doors depicted in the mosaic that decorates the floor, symbolising the seven planets through which the souls of the initiates have to pass.
The Mithraeum of the Seven Spheres is of great importance for the understanding of the cult, because of its black-and-white mosaics depicting the planets, the zodiac and related elements.
The Housesteads Mithraeum is an underground temple, now burried, discovered in 1822 in a slope of the Chapel Hill, outside of the Roman Fort at the Hadrian's Wall.