a mall built on buried ground

Indus Valley (सिन्धु घाटी)

Modern archaeology says five thousand years old. The old stories say older — that what we call the Indus Valley was raised on the bones of a civilization already forgotten. Cities with drainage systems. Standardized weights. A dialect of their own, written in a script that remains undeciphered to this day. And then, without war, without fire, it was simply left behind. Every great trading place eventually becomes a mystery to whoever comes after it. This one, we're building on purpose.

The Great Bath at Mohenjo-daro was watertight — built without a single brick out of place.

For the deeper rabbit hole: Graham Hancock's Ancient Apocalypse episode on the Indus is a good place to fall in.