Why are ancient buildings still standing 1500+ years later, but some buildings built like 30 years ago are falling apart?

Question

Why are ancient buildings still standing 1500+ years later, but some buildings built like 30 years ago are falling apart?

In: Other

Answer 1

Selection and survivorship bias.

The vast majority of buildings built 1500+ years ago are no longer standing, and the vast majority of buildings built in the 1990’s are standing just fine, and of those that aren’t the vast majority were intentionally demolished rather than fell into decay.

Of the ancient buildings that still stand the vast majority were continuously occupied and maintained for that 1500+ year period.

Of the modern buildings that decayed the vast majority were abandoned and left to the mercy of the elements.

TL;DR: If you want a building to last a very long time you need to continually maintain it.