Closer view of the structure of the limestone cliffs, which allowed easy digging to form the burial chamber of pharaohs

Unlike some other types of rocks such as granite which are very tough to dig into, limestone (along with a couple of other types of rocks) is much easier to dig into. This photo shows a cross section of the stones, which seems to indicate that the rock can be dug into more easily than others, and in fact, can even crumble fairly easily.
Learn more about Egypt. Buy the Lonely Planet Guide. Click to buy