[1] The complex geology results from the plate tectonic processes taking place during the Caledonian orogeny involving continental landmasses on either side of the Iapetus Ocean moving together and colliding over a protracted period.
It left behind a landscape of smooth summits above erratic boulders and scree at the foot of cliffs on the eastern side of the mountains, and moraines that created shallow lakes in the cwms.
[2] This area was first colonised in Neolithic times, when Stone Age farmers started clearing the native forests of oak and birch that covered all but the uppermost ridges and summits.
It was in a bog in the northern foothills of Bera Mawr, at a place called Nanhysglain, that Prince Dafydd ap Gruffudd and his family were captured in June 1283.
Another legend has it that the two small lakes nestling below the towering cliffs to the east of Carnedd Llywelyn were haunted and that deformed fish with heads but no bodies lurked in their depths.
A more recent legend records that the two great boulders known as the "Meini Gwynedd" near the summit of Carnedd Llywelyn were lifted there bodily in 1542 from the banks of one of these lakes.
The plants growing on the Carneddau need to be extremely hardy to withstand the snow, frosts, and gales they will encounter during the year and those found by sheltered streams in the valleys are very different from those clinging to crevices on windswept rocks.
Where the sheep are fenced out globe flowers, wood avens, angelica, red campion and roseroot can be found at lower elevations, along with ash, alder, hawthorn, holly and rowan.
The better-drained rocky slopes have bilberry, ling, bell heather and cross-leaved heath and the summit ridge has prostrate dwarf willows, sedges, mosses and lichens.
They have long gone, and, besides the ubiquitous sheep, there are now red foxes, moles, mice, a few pine martens (probably extinct), polecats, and an increasing number of otters.
Common sandpipers nest beside the lakes, the rare twite inhabits the Nant Ffrancon Valley and dotterels are found passing through the upper slopes.