Nice walls! Probably sturdier than any wall a modern country could build for itself. Funnily, this mighty people couldn't defend itself against whatever it was that took them out. Nowadays we build wood structures filled in with soft glass like fibers. Or we use steel and poured concrete which is inferior.
It's practical to build super gigantic structures for our tiny selves. I only buy a computer desk and chair if it is 20x my size. Practical, see? Doorways should always be 3x bigger than any human person could practically use, that way only someone 3x taller could open the door for them. Oh and installing smaller doors for an average human height was normal practice for many buildings of that time, that's all.
Calculating perfection of masonry and construction. So fine, you'd think a machine was used to carve these stones and fit them in place. But no, some very masterful stone masons did this all by hand over the course of ... oh who are we kidding. This civilization had supercomputers and AI like us and robotics. Hm?
Oh they're not around anymore? I wonder what happened to them...
The bigger they were, the greater the fall.
"For All flesh is as grass, And all the glory of man as the flower of grass."