In much of the area bordering the wetlands, an abundance of produce, of great variety, can be cultivated. The green and varied landscape provides good grazing for livestock. In some areas the carboniferous limestone and the Dolomitic Conglomerate have been mineralised with lead and zinc ores. Evidence of early settlement comes from the Sweet Track, which was built from timber felled in the winter of 3807-06 BC, and lowland villages such as Glastonbury Lake Village and hill forts and ancient settlements on hills, many of which date from the Iron Age. From the time of the Romans until 1908, the Mendip Hills were an important source of lead.