In England all the Roman artefacts from 1500 years ago are ruins, while many from only ~500 years later, like the Tower of London are well preserved. Just a few centuries or so of raiding and depredations seperate the two periods of English history.

In some cases Roman architecture was literally dismantled to make something new - the cathedral at St Albans is mostly made from stone taken from Roman buildings.

Things can easily endure that long if well protected, but it’s a long time if they are allowed to fall into ruin (or destroyed).