1. What appears to be a communications/command post connected with military activity is located on the eastern crest of Bryn Tyn-rhos.
It takes the form of an underground room below a shaft entrance, with 21 rung steel ladder, accessed from a raised opening. The shaft is capped with an iron trap-door. It was probably abandoned in the late 1980s/early 1990s (to judge from 'Telecom' labelled control box in sunken room) but is still potentially functional. The site lies within a 15m square fenced enclosure, now derelict.

visited DKL/CSB 13 August 2003

Pumlumon Survey 2002

2. Ponterwyd ROC monitoring post. Opened in October 1963 and closed in September 1991 (information from www.derelictplaces.co.uk). Originally part of a mid Wales network which included similar bunkers at Crosswood, Aberystwyth and Eglwysfach. Across the United Kingdom during the Cold War the Royal Observer Corps were employed to monitor the pattern of nuclear bursts and the spread of radiation from a network of underground posts. Ponterwyd ROC post appears to have the standard configuration of access hatch, fixed survey meter probe, BPI baffle plate and air vent protuding from the ground, while inside observers would monitor a Bomb Power Indicator (BPI) and other instruments at a desk.

T. Driver, RCAHMW, Sept 2015