Glyn Rhonwy Quarry

From the waste tips of Cefn Du Quarry looking out across Llyn Padarn to Dinorwic Quarry on the slopes of Elidir Fawr, with Y Garn and Glyder Fawr to the right (D)


13 March 2011

Glyn Rhonwy, Llanberis

(A) SH 56960 60980; 53.12672°N, 4.13921°W
(B) SH 56392 60760; 53.12460°N, 4.14759°W
(C) SH 56101 60644; 53.12348°N, 4.15189°W
(D) SH 55640 60500; 53.12206°N, 4.15870°W


On the slopes of Cefn Du, in a fairly narrow band extending from the roadside of the A4086 through Llanberis up to the coll with Moel Eilio, there can be found a number of disused slate quarries. Starting from the bottom, these are: Glyn Rhonwy Isaf (with three pits), Glyn Rhonwy Uchaf (two pits), Cook and Ddol (two pits), Cefn Du and, finally, Chwarel Fawr. Quarrying operations in this area date back to the end of the 18th century and had ceased by 1930.

In 1939 the Air Ministry converted the lower pit of Glyn Rhonwy Isaf into a storage facility with a capacity for 18,000 tons of bombs. The store was constructed with two levels, the pit being backfilled with broken slate to a depth of 40 feet over the top of the roof of the upper level. Unfortunately, skimping on costs led to structural defects which caused a massive collapse of about two thirds of the building only six months after it had been built. A train, laden with a bomb payload in excess of 14,000 tons, was in the depot at the time of the collapse. The remaining underground section was thereafter abandoned and the collapsed area used for open storage. The facility was closed in 1956 but was not fully cleared of all explosive material until 1975.

Gwynedd Council owns the land comprising the former Glyn Rhonwy (Isaf and Uchaf) and Cook and Ddol Quarries, and has, for a number of years, been seeking to attract developers to the site. A land reclamation project in the lower parcel of the site (comprising the former Glyn Rhonwy Isaf Quarry) was completed in 2000, which included building an access road and creating various development plateaux. Further clearing of the site and upgrading the infrastructure with the aim of enticing investment is still underway.

Various ambitious schemes for the site have fallen through in the past – including plans in 2002 and 2003 for an indoor snow dome. In 2006 the Guardian reported that eight business groups were competing to develop the site, with one scheme including plans for a ski run, beach, spa, climbing wall, hotel, apartments and timeshares, and another with plans for a mountain bike centre featuring a mile-long cable car ride over the quarries. In 2009 Manchester-based consultancy DTZ put forward details of a scheme for mixed-use development, including business units, residential areas, outdoor leisure businesses and a campsite and caravan park.

An area originally part of the Glyn Rhonwy redevelopment site was sold in 1985 and is occupied by the Siemens Healthcare Diagnostics biotech plant (formerly Euro/DPC).

Glyn Rhonwy was used as a location in the making of the 1988 Ron Howard film Willow.

Orbs in the Bomb Store; Llanberis Bomb Store; Llanberis RAF Reserve Depot (Bomb Store) (Subterranea Britannica); Aerial photo of Glyn Rhonwy Quarry, 1994 (Royal Commission on the Ancient and Historical Monuments of Wales)

Glyn Rhonwy Isaf Quarry - tunnel between lower pit (Bomb Store) and middle pit (A)

Glyn Rhonwy Isaf Quarry - tunnel between lower pit (Bomb Store) and middle pit (A)

Glyn Rhonwy Uchaf Quarry - lower pit (B)

Glyn Rhonwy Uchaf Quarry - upper pit (C)

Glyn Rhonwy Uchaf Quarry - upper pit (C)

5 thoughts on “Glyn Rhonwy Quarry

  1. Interesting post as always Graham, and it’s served as a reminder to me that, I’ve still not visited the bomb store. It’s been on my to-do list for over 2 years now……


  2. Very interesting post, Graham, and a site that I’ve had my eye on for a while now. Yor write up is fascinating and there still seems to be stuff to see.

    Great photos, too!


  3. They should build an eco dome similar to the eden project to encourage people to grow their own food use it as a facility for our local children to learn agriculture and permicultre, use the land but also give back maby have an open plot for locals to plan their veg??


  4. Pingback: Dark Places « GeoTopoi

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