Stories like this make me think of an ancient mercenary Greek general named Xenophon. And how during a retreat across the Persian desert, he stumbled across a massive walled city that was far beyond the capability of any contemporaneous civilization to build.
And yet that city was abandoned, in ruins and being buried by the desert sands, and none of the local inhabitants in the area even had any idea who’d built it.
I like to imagine that’ll be the fate of all these mega-project monstrosities built by slave labour and oil money in places like Saudi Arabia and Dubai. When a combination of lower demand for oil, global warming and the left-over oil money being squandered by princes and petty tyrants eventually causes a collapse of their society.