The rock-carved dwellings of the ancient people of Thamud, predating Ibrahim AS, where entire rooms, chambers, and even beds were carved directly into the mountainside rather than built. The well used by Thamud's she-camel is also still identifiable there.
The Prophet ﷺ passed through al-Hijr on the return march from Tabuk, commanded the army to hurry through without stopping or drinking from its wells, and delivered a warning about entering the dwellings of a people struck by Allah's punishment.