Archaeologists have discovered the world's earliest artificial eyeball in the Burnt city's necropolis (Burnt City, Sistaan, Iran) thought to have been worn by a female resident of the Burnt City. This artificial eye is a hemisphere with a diameter of just over 2.5 cm's. It consists of very light material, probably bitumen paste. The surface of this artificial eye is covered with a thin layer of gilding and is engraved with a circle at its center to represent the iris. The eye includes gold lines patterned like the rays of the sun. A hole has been drilled through the eyeball through which a golden thread is thought to have held the eyeball in place. Microscopic research has revealed that the eye socket of the female remains clear imprints of the golden thread, suggesting that the woman must have worn the eyeball during her lifetime. Experts say that her skeleton dates to between 2900 and 2800 BC.