Sedgemoor is a low-lying area of land in Somerset, England. It lies close to sea level south of the Polden Hills, forming a large part of the Somerset Levels and Moors, a wetland area between the Mendips and the Blackdown Hills. The Neolithic people exploited the reed swamps for their natural resources and started to construct wooden trackways, including the world's oldest known timber trackway, the Post Track, dating to the 3800s BC. The Levels were the location of the Iron Age Glastonbury Lake Village as well as two lake villages at Meare Lake. Several settlements and hill forts were built on the natural "islands" of slightly raised land, including Brent Knoll and Glastonbury. In the Roman period sea salt was extracted and a string of settlements were set up along the Polden Hills.