Agen Allwedd

Agen Allwedd, along with Daren Cilau, dominates the underworld of the Llangattock escarpment. With over 30km of surveyed passages there are a multitude of different trips and sights to experience, from impressive and sculpted dry passages and fine formations to sporting streamways and exciting climbs, there’s something for everyone. Agen Allwedd (or Aggy, as it’s affectionately known), is also a very important bat roosting site with several hundred Lesser Horseshoe bats over-wintering within the cave.


Access is available to any bona fide caving clubs with membership to BCA or similar body. Information rescued in 2019 from the currently offline MLCMAC (Mynydd Llangatwg Cave Management Advisory Committee) website is available below. Please note that some of this information is slightly out of date, but the contacts and access procedures are still valid:

CSS members can access the cave at any time using the club keys held at Whitewalls.

Location and Surveys

NGR:  SO 18768 15861 - what3words: ///exploring.leotard.phantom

Aggy is located along the tramroad footpath, and is roughly a 25 minute walk from Whitewalls. Leaving the cottage simply follow the gravel track until it becomes a footpath then stay on this as it contours around the cliff edges, ignoring the footpath sign heading downhill along the way. You’ll pass a few other caves, the most obvious being Eglwys Faen with its multiple entrances just beyond the information board. Aggy is a gated entrance low on the cliff face at the far end of the track.

Survey Page 1 - Central (click for larger version)
Survey Page 2 - South (click for larger version)
Survey Page 3 - North (click for larger version)

Route Descriptions for Trips in Aggy

The Music Room

The most popular trip in Aggy, and an ideal introduction to the system. Relatively easy caving in a pleasant part of the cave. This route also includes Erse Passage and North Wing.

Route Description

The Grand Circle

A sporty and varied trip with plenty of wetness including Southern Stream, Main Stream Passage and Deep Water, plus Biza Passage and some interesting climbs.

Route Description

Inner and Outer Circle

A journey up Turkey Streamway followed by a circuit of Summertime Series, taking in the Dome of St Pauls, the Swiss Village and the notorious Coal Cellar. Like the Grand Circle, this is a classic Aggy ‘big trip’.

Route Description

Iles Inlet and The Courtesan

A trip via Southern Steam Passage and Priory Road to visit the incredible Courtesan formation. This well-decorated and impressive part of the cave is also the closest point to Daren Cilau.

Route Description


A journey to the southern extremities of the cave to visit the huge stream passage leading to Sump 4.

Route Description

Other Popular Trips in Aggy

  • Sand Caverns - A really interesting part of the cave with large passages and fine formations.

A survey for the cave is available for purchase from CSS at Whitewalls. More photos and descriptions of some of the routes are available on the website.