Nant Ddu is on the other side of the Beacons to the other communities served by Llanfrynach Community Council.
Its connection with Cantref dates from the days when both communities were in the same parish, with the peak of Pen y Fan right in the middle!
Today the community of Nant Ddu is no more than a handful of residents – but the hamlet is home to three of the great landmarks of the Beacons, the reservoirs built in the late 19th century to provide clean water from the Beacons to the burgeoning industrial South Wales valleys and Cardiff.
The other major landmark on the A470 is the Nant Ddu Lodge.
The old Church of Nant Ddu is no longer standing but the iron gates are still there, protecting the old churchyard.
Farms in Nant Ddu and in Cantref share grazing rights on the Beacons and regularly farmers on both sides work together, gathering their sheep and ensuring they return to the right homes for lambing, shearing, dipping and tupping.