This mortar emplacement is one of a line of three aligned accross the Ogwen Pass, a strategically important route between Bethesda and Capel Curig. It forms part of the Scheduled Ancient Monument, Nant Ffrancon anti-invasion defences, dating to the early period of the Second World War. It comprises a static 29mm spigot mortar emplacement consisting of concrete pedestal mounted on a circular foundation.

Sources include:
Cadw, 2007, Nant Ffrancon Anti-invasion Defences

N Vousden, RCAHMW, 22 January 2014