The area to the south east of Caban Coch Reservoir.
There are plenty of cairns, some are very well preserved with central cists.
Gro Hill is a short walk from Crugiau Bach Stone Circle and Cairns. Walk from the Elan Valley Visitor Centre up past Caban Coch Dam and Nant y Gro Dam to get to Gro Hill.
Map Ref: SN925 620
Tel: 07870954997