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In discussing the possibility of lost civilisations, the question is often asked: if there was an advanced civilisation in antiquity – say, more than 10,000 years ago – how much evidence would actually be left for us to find? The above video covers this in asking the question, what would happen if humans disappeared from the planet:

After 10,000 years, the only reminiscence that people were here someday, will be the remains of a few stone constructions, among which [would be] the pyramids in Egypt and the Great Wall of China. Mount Rushmore National Memorial will be there almost intact for several hundreds of thousands of years.

(via Gizmodo)