Sabu Disk: A mysterious 5,000-year-old Egyptian stone sculpture that looks like a hubcap

This delicate stone vessel was discovered in 1936 in the tomb of Sabu, an ancient Egyptian official buried in the Saqqara necropolis during the first dynasty period. When it was found, the disk was in pieces. It has since been reconstructed and is in the collection of the Egyptian Museum in Cairo.

Sabu's mastaba, a rectangular tomb with sloping walls and a flat roof, was excavated by British Egyptologist Walter Emery. In his publication describing the Saqqara tombs, Emery wrote that the burial chamber had been looted for its jewelry and precious metals. But Sabu's skeleton was intact inside a wooden coffin, and his tomb was filled with dozens of stone and pottery vessels, flint and copper tools, the remains of two oxen, and a unique bowl.

Emery described the Sabu Disk as an ornamental tri-lobed bowl that measured 24 inches (61 centimeters) in diameter and 3.9 inches (10 cm) tall. The bowl was carved out of metasiltstone, a sedimentary rock that has undergone some metamorphism.

Related: Hornelund Brooches: Viking age gold ornaments mysteriously buried in Denmark 1,000 years ago

According to Egyptian archaeologist Ali El-Khouli, flat and wide stone bowls were common in the first to third dynasties of ancient Egypt. But this particular bowl found in Sabu's tomb is unusual because of the three thinly carved and curving wings that rise from the edge of the disk. When viewed from above, this decoration is suggestive of a modern steering wheel, propeller or hubcap.

The Sabu Disk's unique design has led to numerous theories about the item's purpose, ranging from part of a water turbine to a piece of a hyperdrive from an alien spaceship. One recent theory even suggests the disk was used as a "mash tun," a vessel that holds grain and hot water for making beer.

But the most likely explanation is that the Sabu Disk had a similar purpose as other wide, flat bowls in ancient Egyptian culture: It probably held food or oil. The delicate nature of the metasiltstone and carving, though, suggests that the bowl was not for everyday use and may have been placed in Sabu's tomb as an offering for the afterlife.