The Egyptian pyramids erupting from the sands at Giza are a testament to human ingenuity and engineering. Raised to mark the tombs of ancient pharaohs, these great structures have stood for thousands of years.

But over the millennia, the pyramids have changed, largely due to construction workers’ repurposing of in-demand materials and looting. So what did the pyramids look like when they were built?

When the ancient Egyptian pyramids were originally erected, both in Giza and elsewhere, they didn’t look sandy brown as they often do today; rather, they were covered in a layer of shiny sedimentary rock.

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“All the pyramids were cased with fine, white limestone,” Mohamed Megahed (opens in new tab), an assistant professor at the Czech Institute of Egyptology at Charles University in Prague, told Live Science. The limestone casing would have given the pyramids a smooth, polished layer that shined bright white under the Egyptian sun.

Read more: Live Science