Known. One stone grave at Hattusa is the best preserved of this type found there so far.
The graves are at Hattusa, in central Turkey, once the Hittite capital. These graves are not from the Hittite age. They date from the late 4th century BC to the 3rd century BC, about 2,300 years ago. The best-kept tomb has a ring of stone about seven metres across, and an inner stone grave big enough for an adult. The skeleton was mostly intact. A knife lay by the right shoulder.
The page says it is not yet known whether the knife was a grave gift, or whether the person was a man.