Originally the term "Cambrian Mountains" was applied in a general sense to most of upland Wales. Since the 1950s, its application has become increasingly (and arguably illogically) localised to the geographically homogeneous Mid Wales uplands known in the Welsh language as the Elerydd (which extend from Pumlumon to Mynydd Mallaen).
This barren and sparsely populated wilderness is often referred to affectionately as the Desert of Wales.
The highest point of the range is Pumlumon. The area includes the source of the River Severn and River Wye, and has been proposed as a National Park. It is the type of locality of the Cambrian period of the Paleozoic era (542-488Ma).