Ogof y Daren Cilau

Ogof y Daren Cilau
Caver crawling into entrance
Location	Llangattock escarpment
OS grid	SO20521530
Depth	192 m (630 ft)
Length	27 km (16.8 mi)
Entrances	2
Difficulty	tortuous entrance series
Access	free
Translation	Cave of the outcrop with [many] nooks (Welsh)
Cave survey	zoomable plan drawing

Ogof y Daren Cilau is a cave system in the limestone escarpment on Mynydd Llangatwg (Llangattock Mountain), which is south of Llangattock village and above Crickhowell in south Powys, Wales.^[1] The escarpment is the remnant of quarrying that had begun by the mid-18th century and initially provided limestone for building and agriculture as a fertiliser, and subsequently for the blast furnaces of the local ironworks as a flux.^[2] The cave system was discovered in 1957 and is one of the longest in the United Kingdom. The system is next to the Ogof Agen Allwedd system.