I live in a city that was founded by the Romans around the time of Christ. But has been abandoned and rebuild a couple of times (by a.o. Charlemagne). Everytime something is built, dug, or torn down, they find old or ancient foundations. Sometimes underneath old foundations. Fortresses underneath mideaval cellars, city walls below a casino. A Bathouse in a parking garage.

It makes building stuff, quite cumbersome. And I can only imagine the amount of ancient foundations that have been quickly eradicated, so that a real estate developer could keep on schedule to maximize profits.