When the Emperor Constantine became a Christian,Christianity was made the official religion of the Roman Empire and the catacombs were visited by many pilgrims. But by then,the Roman Empire was being attacked by warlike people from the East. The Goths conquered the city in AD 410,and the entrances of the AD 410 catacombs were filled up in order to protect them. By the 12th century , everybody had forgotten about them. They had been so well hidden that it was not until 1578 that one was found, and the Roman authorities began to uncover them.