I've seen and heard things about people exploring old cities that are underneath the new cities. Like fully constructed buildings and cities under modern ones. How does this happen? Do they just build on the roofs of the old city and bury them? Its probably a dumb question but it absolutely blows my mind that there could be an entire city beneath the one that we know and why people would just want to bury and start over in the first place.
There is always more to be said, but while you are waiting for fresh responses to your query, you might like to review these earlier threads which also address the question:
Why is it that so many historical sites and artifacts are buried underground?, led by u/UndercoverClassicist
Many archaeological sites of settlements are often described as having "layers". Are these literal layers or an archaeological term?, led by u/Aerandir