"Bimmah Sinkhole (Arabic هـويـة نـجـم Hawaiyat Najm) is a water-filled depression, structurally a sinkhole, in the limestone of eastern Muscat Governorate in the Sultanate of Oman. A lake of turquoise waters, it is 50 m by 70 m wide and approximately 20 m deep. It is only about 600 m away from the sea, between the coastal towns of Ḑibāb and Bimmah. The sinkhole was formed by a collapse of the surface layer due to dissolution of the underlying limestone. However, locals believe that it was created by a meteorite, ‘Hawaiyat Najm’, which translates to ‘The Falling Star’ in Arabic, and hence the name"
The Great Pyramid is made up of around 2.3 million limestone blocks