SAUDI ARABIA: Nomadic pastoralists roaming northern Saudi Arabia 7,500 years ago built an unusual stone platform near the oasis site of Dumat al-Jandal. The trapezoidal monument was first constructed in the middle of the 6th millennium B.C., but was modified several times, eventually reaching a length of 115 feet. In and around the structure, archaeologists discovered several burials that suggest the stone monument was an important place of commemoration that was used for funerary and social rituals for thousands of years.