Link

Pen-y-Foel
Hillfort
Coflein

Aerial photo of the site.

Description from Coflein:

A sub-rectangular enclosure, about 165m east-west by 124m, upon the summit of Pen-y-Foel; defined by a bank and ditch above steep slopes on the north and east, on the west is a further rampart and ditch, about 48m from the inner line.