Situated to the north of Fochriw and west of Rhymney, the area known as Nant Llesg has a proud history of coal and iron mining. Approximately 41% of the operational area of the site has previously been surface mined and 100% of the area has been historically mined by underground methods.
However, the underground mining legacy has left the area with many issues. Nant Llesg is home to old mine workings, including more than 120 known potentially hazardous mine shafts and entrances. Other parts of the site are currently covered with colliery spoil tips and as such may contain other points of danger.