Lying as a sleeping giant in a bed of granite, the Unfinished Obelisk in Aswan, Egypt is an incredible look at the building methods of these monolithic monuments. It would have measured about 137 feet (42 meters) if completed and is estimated to weigh around 1,200 tons. It’s thought that the female pharaoh Hatshepsut commissioned the work during the 18th dynasty, more than 3,500 years ago.
Carving the monuments directly in the bedrock was a common technique, and stone balls were used by masons to pound out any imperfections until the surface was smooth. There are still examples of these Dolerite balls, on-site as Aswan. Harder than granite, the Dolerite wouldn’t crack or break after repeatedly pounding against the stone surface.
One of the more interesting aspects of the Unfinished Obelisk is that it allows us to see just how they would have liberated the mammoth structure from the bedrock had it not cracked. It sounds unbelievable, but wet wood was the answer. Workers carved small cavities in the stone, creating a line that is not unlike a perforated piece of paper. The slots were filled with sun dried wooden wedges. The wedges were then repeatedly soaked in water, and believe it or not, the expansion of this wood would cause the carved rock to break free from its home.
Info via : https://mymodernmet.com/