Following the post-glacial flooding of the Persian Gulf basin, debris from the Tigris–Euphrates river formed a substantial delta, creating most of the land in present-day Kuwait and establishing the present coastlines. Historically, northern Kuwait was part of ancient Mesopotamia. One of the earliest evidence of human habitation in southern Kuwait dates back 8000 B.C. where Mesolithic tools were found in Burgan. The Neolithic inhabitants of Kuwait were among the world's earliest maritime traders. During the Ubaid period (6500 BC), Kuwait was the central site of interaction between the peoples of Mesopotamia and Neolithic Eastern Arabia, including Bahra 1 and site H3 in Subiya. One of the world's earliest reed-boats was discovered at site H3 dating back to the Ubaid period. Other Neolithic sites in Kuwait are located in Khiran and Sulaibikhat. Mesopotamians first settled in the Kuwaiti island of Failaka in 2000 B.C. Traders from the Sumerian city of Ur inhabited Failaka and ran a mercantile business. The island had many Mesopotamian-style buildings typical of those found in Iraq dating from around 2000 B.C.