There is marble from the Colosseum all over Rome.
Meaning the Colosseum was a ruin for two hundreds years.
Whenever some Rome resident was doing work on their house they would go over to the Colosseum and remove the marble and anything else they could. It was cheaper then buying newly quarried marble/materials.
This was told to me by the guy who gave us the tour of the site. He said there is marble today in peoples houses in Rome that came from ancient Roman buildings like Nero’s palace.
They recycled !
Indeed, just got back from Italy and heard the same stories from the guides. Apparently it was common practice.