Erir, Heremi, Heremus, Herir, Heriri, Reir

The name by which Geoffrey refers to Yr Wyddfa Fawr or, more usually nowadays, Mount Snowdon.

This is the area where Vortigern sought to build a fortress. It is also called Dinas Emrys. It may be related to the mountain Aravius, where Arthur slew the giant Ritho (Rhitta).

According to Tennyson, it was rumored that the infant Arthur had been found by a forester on the mountain.