Megalith mysteries

A lot has been said and written about stone structures that have survived from the distant past into our own time. The larger they are, the more impressive they seem to us, leading to speculation about the tools used to create and erect them:

How could a perfectly rectangular stone block weighing 100+ tons have been created and moved into place, fitting perfectly in with similar blocks, without the use of modern types of machinery?

This has led to speculation about these monuments being silent reminders of ancient advanced societies that expired a long time ago.
Perhaps not unlike our present day one.

That is a tempting conclusion, but to me there is a missing piece of evidence for this: If our society was to have an apocalyptic breakdown of some kind, the remnants of our transportation system earthworks would survive into the distant future.

Apart from the Roman road system and aqueducts, I don’t think anything like that has been discovered to date.