In the northwest of Wales you'll find a long belt of Cambrian slate which was formed about 500m years ago. The line stretches from the Nant Ffrancon valley in the east to Nantlle Valley in the west.
Some of the largest and most productive slate quarries in the world were situated along this belt. The region was known to have "roofed the 19th century world", which in its turn had a significant effect on the lives of the region's people and communities as well as the landscape with its traces still found today.
In the east the slate was garnered through open quarries using the gallery method while in the west slate beds were found beneath the floor of the valley. It was the depth of the slate beneath the valley floor which influenced the quarrying techniques of Nantlle. And the only way to obtain the rock was by digging down and creating large pits.
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There was a large number of very small quarries in Dyffryn Nantlle – a situation which was brought about by numerous landowners. Over time amalgamations and takeovers would create larger units such as Dorothea quarry. In 1820 Dorothea was opened and remained in production until 1970. The land the quarry stands on was owned by a man called Richard Garnons but the main driving force for quarrying in the valley was William Turner from Lancaster.
The original name of the quarry was Cloddfa Turner but it was renamed as Dorothea after Garnons' wife. The workings grew out of a series of smaller workings with names such as Hen Dwll, Twll Bach, Twll y Weirglodd, Twll Coch, and Twll Fire. Over the years these pits were deepened and amalgamated into the large flooded pits that we see today.
By the 1840s production at Dorothea had built up to about 5,000 tonnes per annum. By the 1870s, however, it had reached more than 17,000 tonnes – in excess of triple the amount it had created 30 years previously. Although the future was looking good for Dorothea it was facing serious flooding problems.
In 1884 several men were drowned when the pit was engulfed. In 1895 the Afon Llyfni, which flowed through the valley, was realigned and deepened to flow to the south of the slate workings. This cured the flooding problems to some extent but, as the workings deepened, the need to continually pump out water became a constant drain on the quarry's profits.
In 1904 the decision was taken to install a Cornish beam engine on site to replace the waterwheels. The remains of the engine can still be found in the village of Talysarn. As the quarries of the Nantlle Valley continued to grow it led to the removal of the old Talysarn village.
It was decided that the village would be relocated to the west where it remains today and is home to just under 2,000 people. But some of the old village's buildings remained in use by the quarries and their ruins can still be seen to this day. This was followed in 1927 by the relocation of the main road to the south of the valley but the route of the old road can still be followed.
Today photos show that nature has reclaimed the old Talysarn village at Dorothea quarry. According to the author of Wild Guide Wales, Daniel Start, what remains today of the ruins is like a 'Welsh Angkor Wat'.
"Only the baboons are missing," he wrote. "It's a vast, wild site with many fascinating, overgrown ruins, including a Cornish beam engine and the overgrown remains of the chapel at Plas Talysarn."
Plas Talysarn, or Talysarn Hall, was built during the 18th century and was later modified and extended in the 19th and early 20th centuries. The house was three stories high over a basement. Although most of the roof of the hall is now missing some timbers have survived over the south facing front wall.
Nearby you'll find the entrance to what was once a stable block and kennels, which was later modified to a shower block for the quarrymen. You'll also find a former boiler house with its roof largely gone but two deteriorated Lancashire boilers remain.
Other neighbouring buildings are covered in moss and tree roots. Like many other quarry pits production dropped significantly after the start of the Second World War. The quarry was eventually closed in 1970. Dorothea Quarry has long since flooded with the lake more than 100m deep in places. The site is now part of the Slate Landscape of Northwest Wales World Heritage Site, which was announced by Unesco in July 2021.
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