Sounds like the Basilica San Clemente, about 5 minutes up the hill from the Colosseum. 3 levels of history.
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 !
I thought there was a topic about that site, but found bupkis. Looks like I’ve got some sitting on my butt and watching the stream to do. 😁 IOW, do difference from other days.
https://search.brave.com/videos?q=Basilica%20San%20Clemente