Another example is their mastery of acoustics. I remember visiting ruins of Roman amphitheaters when I younger, and getting surprised at how they had managed to design them so that the audience would clearly hear what was happening on stage, even from great distance.

I was told it was not entirely clear to us what key principles they were following to get the acoustics working so well and that a lot of their wisdom had been lost to us.

It was like 25 years ago, so I hope we've made progress in rediscovering some of these techniques. But still...