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

All people above are right, yet I hove something to add. Most of ancient buildings, that we can see today, were made to stand a long time. There are usually temples or palaces or other important buildings that demonstrate power and knowledge of the civilization.
You shouldn’t compare them to common cheap houses made of shit and sticks. Compare them to some super expensive government’s complex made of good steel and best concrete. Such buildings don’t collapse in 30 years.