When the Romans settled in Britain in 43 CE they could hardly have imagined that the small agricultural settlement of Londinium on the Thames would eventually become one of the biggest cities in the world. Its people worshipped then in small buildings like the Mithraeum, but over the next two thousand years cathedrals, synagogues, churches, mosques and temples changed the city skyline. Destroyed many times--by fire, disease, internal revolution and...