Barrel vaulting was known and utilized by early civilizations, including ancient Egypt and Mesopotamia. However, it apparently was not a very popular or common method of construction within these civilizations. The Persians and the Romans were the first to make significant architectural use of them. The technique probably evolved out of necessity to roof buildings with masonry elements such as bricks or stone blocks in areas where timber and wood were scarce. The earliest known example of a vault is a tunnel vault found under the Sumerian ziggurat at Nippur in Babylonia, ascribed to about 4000 BC, which was built from fired bricks amalgamated with clay mortar. The earliest tunnel vaults in Egypt are found at Requagnah and Denderah, from around 3500 BC in the predynastic era. These were built with sun-dried brick in three rings over passages descending to tombs with a span of only two metres. In these early instances, the barrel vault was chiefly used for underground structures such as drains and sewers, though several buildings of the great Late Egyptian mortuary palace-temple of Ramesseum were also vaulted in this way. Recent archaeological evidence discovered at the Morgantina site (in the province of Enna) shows that the aboveground barrel vault was known and used in Hellenistic Sicily in 3rd Century BC, indicating that the technique was also known to ancient Greeks.