The cliffs are part of a huge rock wall called the Tuwaiq Escarpment that runs for over 800 kilometres through central Saudi Arabia. It is roughly the same shape as a giant comma that someone has drawn in the desert.
The flat plain below the cliffs used to be the bottom of an ancient sea. If you look closely at the rocks, you can spot fossilised shells from creatures that swam here long before there were any deserts. Saudi Arabia has not always been hot and dry - it has had several huge changes of climate over millions of years.
The view from the top stretches for around 50 kilometres on a clear day. Old camel-trade routes ran along the base of the cliffs, because the flat plain was the easiest place to walk for hundreds of kilometres.
The cliffs face west, so they are most beautiful at sunset - the rocks turn pink and orange, and the shadow of the cliff stretches further and further across the plain below. Families from Riyadh often drive out to watch the sun go down.