9,000-year-old rock art of people swimming in what's now the arid Sahara

Name: Cave of Swimmers

What it is: A series of rock paintings depicting a group of people swimming

Where it is from: Egypt's Western Desert

When it was made: Between 6,000 and 9,000 years ago

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What it tells us about the past: Thousands of years ago, the Sahara Desert was not the dry, sandy landscape we know it as today — it was a lush, green oasis. In fact, the sandstone-rich Gilf Kebir plateau, which stretches from southwestern Egypt into southeastern Libya and is where the rock art resides, offers further evidence that this swath of land was once accessible to bodies of water and not always a barren desert.

In 1926, the remote area was mapped by European cartographer László Almásy who stumbled upon two "side-by-side shallow caves" adorned with hundreds of rock paintings of Animals and humans, including handprints that would have been created by someone "blowing pigment onto the rock face over splayed fingers," according to The British Museum.