Caer Blaen Maenog comprises the remains of a well preserved earthwork defended enclosure, and is sited some 600m south-south-east of St Llawddog's Church, Penboyr (NPRN 310024) and associated motte and bailey castle, Tomenlawddog (NPRN 303730). The enclosure is located on a north-facing inland promontory, above steep slopes that mark the defensive circuit on the east and north-west sides. The south-west side is defended by a close set series of three large banks with intervening ditches. The inner bank is the largest and measures 70 meters in length, 5 meters in height and 10 meters in width. The middle bank measures 95 meters in length, 3 meters in height and 9 meters in width. The outer bank measures 110 meters in length, 2 meters in height and 9 meters in width. Unusually, the steep slope at the northern point of the promontory is also defended by a bank and ditch. The bank measures 2.5 meters in height and the ditch measures 4.5 meters in width and 1 meter in depth.
Source: Cadw scheduling description. F.Foster/RCAHMW 11.02.2009