The slopes of the Glyderau also include the lake Llyn Idwal, and a number of classic climbing areas such as Rhiwiau Caws.

The Glyderau were formed in the Ordovician period about 500 million years ago as the result of two land masses moving together and causing the Snowdonia massif to rise up.

The ice scarred the surrounding cliffs, hollowed out the bed of Llyn Idwal and dumped rocks and other material that formed moraines at its foot.

Tryfan, Glyder Fach and the cliffs around Cwm Idwal offer rock climbing with routes ranging from those suitable for beginners to those requiring great technical expertise.

Because of the scientific interest of this valley, sheep have been excluded from it to allow the native plants to flourish and it has been made into a national nature reserve.

Plants growing in the water or on the damp ground nearby include awlwort, pillwort, waterwort and spring quillwort (Isoetes echinospora).

The traveler Thomas Pennant, writing in the 1780s, stated that the local shepherds were in awe of the lake believing it to be "the haunt of Demons, and that no bird dare fly over its damned waters".

The power is conveyed through underground cables to join the grid so as to have little visual impact on the Snowdonia National Park skyline.

There are eight tenanted farms on the estate and the National Trust is responsible for the maintenance of footpaths and drystone walls, some of which date back many hundreds of years.