Only_Razzmatazz_4498 t1_je4rxm8 wrote

The Hagia Sophia mosque in Istanbul that started life as a Byzantine (eastern Roman Empire) church is an example of one used and maintained over the millennia. Also there is a church in Rome (Pantheon) that started life as a Roman gods church (pantheon lol) and has one of the oldest and largest concrete self supporting domes with an opening up top (oculus) for light. I think the doors are the original also.

There might be other counterexamples but as someone said it all depends on whether the structure found other uses and possibly at least in the western world the church was the only large organization with the resources to maintain empire type structures.