Here you can see how so much was reused- ancient columns turned into a colonnade for the courtyard of the church. It’s interesting to see that the ancient Romans took great care to use bricks that were regular (and stamped) in shape, uniform and balanced architectural elements,etc. By the 4th century when churches and other religious structures needed to be built in a hurry not so much care and a lot of “recycling” took place. We saw floors that contained all kinds of stones including parts of inscription stones used for flooring. Remember, once Constantine became a Christian they needed facilities.