The Red Pyramid, built around 2600 BCE, was the world's very first true, smooth-sided pyramid.

While Djoser's pyramid looked like a giant staircase, Egyptians soon wanted smooth, straight walls. They tried and failed a few times, but finally succeeded with the Red Pyramid of King Sneferu. Completed around 4,600 years ago, it set the standard for all the famous pyramids that came later, including the Great Pyramid of Giza. It proved that builders had mastered the math and engineering needed to make massive, perfectly sloped stone mountains.