Mynydd Twyn-glas

Mynydd Twyn-glas is a mountain in Caerphilly rising to about 472 meters with steep slopes covered by conifer forests and a broad summit plateau. The peak sits between two distinct knolls that are higher than the surveyor's marker at the top.

This peak formed during the late Carboniferous Period when coal seams were deposited along its eastern slopes. The geological processes that shaped it over millions of years remain visible in the rock and terrain you walk across today.

The Welsh name means 'hill of the blue knoll', reflecting how local communities named landmarks based on what they saw in the landscape. Walking across the summit reveals this connection between language and the physical features that surround you.

The hill is connected to neighboring towns by several public footpaths and is easily reached from surrounding areas. Watch for slippery slopes after rain and plan for changing weather conditions, as the summit can be exposed to strong winds.

A significant landslip on the Mynydd Henllys side of the mountain shows the dynamic geological forces still shaping this place. This movement of earth beneath the surface reminds you that the land itself continues to shift and change over time.

Location: Caerphilly County Borough

Elevation above the sea: 472 m

GPS coordinates: 51.67420,-3.07160

Latest update: December 14, 2025 18:40