With a long history of slate quarrying and its vast mountain ranges, North Wales offers a lot of scope for urban exploration. Urban might not be the most appropriate word but I can’t stand the abbreviation of rural exploration. Rurex just sounds like someone doing a poor impression of a Chinese person talking about condoms. 

In this part I will talk about Dorothea quarry, one of my favourite places to explore. It’s a huge site, set around five lakes, which are actually former quarry pits that have gradually filled up with water. Anyone who dives has probably heard about Dorothea, as the largest lake, Twll Mawr, is a popular and dangerous site to dive. The lake is over 100 meters deep and there have been a few deaths. In the decade 1994-2004, 21 divers lost their lives.

Twll Mawr
Twll Mawr

Quarry operations started in 1826 and continued until 1969, when the demand for Welsh slate had all but ended. What’s left now is 300 acres of interesting quarry buildings, tunnels and houses to explore. Some of the ruined buildings were actually part of the original village of Talysarn, which was relocated to its current location when the quarries grew.

There are a number of routes into the quarry. The easiest being from the villages of Talysarn or Nantlle. You can’t miss the quarry as the mountains of slate are hard to ignore.

Many of the buildings have been swallowed up by woodland, so if you go during the summer months you will need to do some serious looking to find them. Also hidden in the woods is an interesting tunnel. It goes back for around 150 meters or so before ending in a collapse/fill-in and is covered in delicate stalactites. Please don’t snap them off if you find it as they take such a long time to form. If you make it to the end of the tunnel, look on the right hand side and you will see a small crawl space that turns 90 degrees and leads on for several meters before also ending in a collapse.

Stalactites forming on cave roof

One of the most obvious buildings is the pump house, which used to contain a Cornish beam engine to continuously pump water out of the quarry pits. It was installed in 1904 and was in use until 1951, when it was replaced with an electric pump. Much of the pump house is intact, including the boilers and the pump shaft – so take care.

Dorothea also has two large ‘pyramids’, which were originally used as the bases for the chain inclines and allowed the waste rock to be tipped behind them. Under one of the pyramids you will find what’s left of the old tramway which would have once joined the Nantlle railway.

Tramway tunnels under the pyramid

Another interesting quarry building is the ruined mill, where slate would have been cut and processed. The outside walls are almost completely gone, but many of the original features remain, hidden amongst the trees that now grow inside.

Near to the main path which circles the quarry is Plas Dorothea, a once grand Victorian mansion which is now in ruins. There are some nice arches behind the hall and if you turn left in the gap in the wall there are some particularly interesting rooms that have large tree trunks growing through them. Through the Rhododendron bushes opposite the hall are the remains of a large ornamental fountain.

There is so much to see at the quarry, it is difficult to list all of the points of interest and I often discover new things on every visit. If you are in the area it is definitely worth a visit and if you would like a guided tour, then please pop me an email. I live very close to the quarry and would be happy to show you around.