LONDON — An ancient temple to Mithras in the heart of the city of London was re-opened this month after a significant amount of renovation. The original temple was built in 240 A.D. by the Romans in order to honor the Middle Eastern god Mithras, who was popular among soldiers. It was not the only Mithraeum built in the UK; others include the Carrawburgh Mithraeum dated to the 3rd century Mithraeum,the Rudchester MIthraem on Hadrian’s Wall, and the Caernarfon Mithraeum in Wales, which was featured in the Merlin series of novels written by Mary Stewart. These temples, like the one in London, were all situated underground. In 2010, the Bloomberg company opened its new European headquarters on the very site on which the original London Mithraeum had once been.