Wrysgan quarry

Cwmorthin quarry was a slate quarry west of the village of Tanygrisiau, north Wales. Quarrying on the site started in 1810. In 1860 it was connected to the Ffestiniog Railway. In 1900 it was acquired by the nearby Oakeley quarry and the two were connected underground. In 1970 it closed along with Oakeley. There was small-scale working in the 1980s and 1990s, and the mine finally closed in 1997.

Moel-yr-hydd is a subsidiary summit of Moelwyn Mawr in Snowdonia, North Wales and forms part of the Moelwynion. (Strictly the mountain is not actually in the Snowdonia National Park as it falls within the exclusion "hole" around the former slate town of Blaenau Ffestiniog.) The mountain overlooks the village of Tanygrisiau and Tanygrisiau railway station (a halt on the Ffestiniog Railway) from where the mountain can easily be ascended.From the 1830s until 1946, Wrysgan Quarry was worked on the north east flank of the mountain. Substantial underground chambers were driven beneath the summit.

Tanygrisiau railway station (grid reference SH683449) is a passenger station on the narrow gauge Ffestiniog Railway The line was built in 1836 to carry dressed slate from Blaenau Ffestiniog to Porthmadog for export by sea but official passenger services began in 1865. The station serves the slate mining village of Tanygrisiau and was opened in March 1866. It closed to passengers on 15 September 1939. The new station opened for passenger traffic on 24 June 1978 and was the passenger terminus until 25 May 1982. Tanygrisiau station is at a height of 669 ft (204 m) and a distance of 12 miles 10 chains (19.5 km) from Porthmadog. The new station is on a different alignment and grade from the old, the two alignments joining just to the north of the Blaenau end of the station. The old line was on a continuous downward gradient from that point through the station, but the new line is on an uphill gradient (to pass the nearby power station) and is more sharply curved. One of the old buildings still remains, visibly lower than the new trackbed. Tanygrisiau station has an operational passing loop but is normally operated as an unstaffed halt and trains only call on request. Intending passengers are advised to check with the Ffestiniog Railway Company before embarking on their journey. The station is close to the Cwmorthin water falls, and the train passes Tanygrisiau hydro-electric pumped-storage power station and Llyn Ystradau.

The Ffestiniog Power Station (Welsh pronunciation) is a 360-megawatt (MW) pumped-storage hydroelectricity scheme near Ffestiniog, in Gwynedd, north-west Wales. The power station at the lower reservoir has four water turbines, which can generate at full capacity within 60 seconds of the need arising. The scheme has a storage capacity of around 1.44 GWh (5.2 TJ) at maximum output for four hours, and the capacity to power the whole of North Wales for several hours.The station, commissioned in 1963, was the first major pumped storage system in the UK. The upper reservoir is Llyn Stwlan, 170,000 cubic metres (6,000,000 cu ft), which discharges 27 cubic metres per second (950 cu ft/s) of water to the turbine generators at the power station on the bank of Tanygrisiau reservoir. The building of the lower reservoir increased the size of Llyn Ystradau and flooded the route of the Ffestiniog Railway which had to build a deviation around the reservoir and power station. The plant is operated by First Hydro, a UK company owned by a joint venture of International Power and Mitsui & Co., and has an average efficiency of 72–73%, i.e. it uses 39% more electricity (when pumping the water back up to the Llyn Stwlan) than it actually produces.

Deep Sleep is an underground hotel located in Wales. It is built 1,375 feet (419 m) below ground level, inside an abandoned mine in Cwmorthin quarry in Snowdonia (Eryri) National Park. It was opened in April 2023 and claims themselves as the deepest accommodation in the world. The mine where the hotel is located was abandoned and left to rot in the mid-twentieth century.

Conglog quarry was a small enterprise situated to the north-west of Tanygrisiau, near Blaenau Ffestiniog in Wales. It was overshadowed by the much bigger Rhosydd quarry a little further to the west. It was active from 1854 to 1910, and was operated by an individual, two partnerships and four separate companies over this period.

Tanygrisiau is a village and area within Blaenau Ffestiniog in the upper end of the Vale of Ffestiniog in the county of Gwynedd, north-west Wales (52°59′12″N 3°57′25″W). It can be found along the southern side of the Moelwyn mountain range and dates to around 1750. It joins onto the semi-urban area of Blaenau Ffestiniog, and is in the community of Ffestiniog; located between 650 feet (200 m) and 750 feet (230 m) above sea level. it is in the electoral ward of Bowydd and Rhiw which had a 2011 census population of 1878. The village itself has a population of around 350.

Moelwyn quarry is a defunct slate quarry located to the south of the village of Tanygrisiau, north Wales. Some initial prospecting was carried out in the 1820s and again in the 1840s, but it was 1860 before a company was formed, and chambers were excavated. The quarry was never a financial success, and operated sporadically until its demise in 1897. Despite the poor results, a spectacular series of seven inclines were constructed, to enable slates to reach the Ffestiniog Railway. The quarry was hampered by lack of a good water supply, and the mill was constructed between inclines 4 and 5, where water could be obtained from Llyn Stwlan. As in many quarries, barracks were provided, but these were occupied by whole families, living on the mountain, rather than used as lodgings for the quarrymen during the working week. Even in its remote location, there was still a concern for education, with basic literacy classes being run in the 1860s.

Allt-fawr is a mountain in Snowdonia, North Wales and forms part of the Moelwynion group. It is on the internal border of Snowdonia National Park, and overlooks the town of Blaenau Ffestiniog, with its numerous slate quarries, as well as Llyn Ystradau and Ffestiniog Power Station in Tanygrisiau. On the northern slope of Allt-fawr is the Oakeley Quarry, the world's largest underground slate mine. On the southern slope is the large Cwmorthin Quarry. These two mines are joined underneath the summit of Allt-fawr and the extensive chambering and adits are visible on the surface of the mountain where underground workings have collapsed.Between 1974 and 1997, the Gloddfa Ganol tourist attraction operated within the Oakeley Quarry on the south slope of the mountain.

Nyth-y-Gigfran quarry (sometimes spelt: Nith-y-Gigfran or Nidd-y-Gigfran; sometimes known as Glan-y-Pwll quarry) was a slate quarry in the town of Blaenau Ffestiniog, North Wales. It was located about 300 feet (91 m) above the settlement of Glan y Pwll, south of what was to become Blaenau Ffestiniog. The quarry was sited on the steep cliffs that form the eastern edge of Allt-fawr and was entirely underground. The quarry opened around 1840 and became part of the Oakeley quarry in the 1880s; this in turn closed in 1969.

Rhosydd quarry was a slate quarry in the Moelwyn mountains, northeast of Porthmadog in North Wales. Small-scale working of the site began in the 1830s, but was hampered by the remote location, and the lack of a transport system to carry the slates to markets. The Rhosydd Slate Company was formed in 1853, and became a limited company in 1856. Transport was made more difficult by the attitude of the Cwmorthin quarry, through whose land the most obvious route to the Ffestiniog Railway ran. A solution was found in 1864, with the opening of the Croesor Tramway, to which the quarry was connected by one of the longest single-pitch cable-hauled inclines in Wales. Huge amounts of money were spent on development work, and the company, unable to make adequate returns, went into voluntary liquidation in 1873. The quarry was auctioned in 1874, and the New Rhosydd Slate Quarry Company Ltd. was formed. Unlike its predecessor, the directors were all Welsh, and three-quarters of the shareholders were also from the local area. The quarry prospered for a while, but then profitability declined, and in 1900, a large section of the underground workings collapsed. The job of opening up new areas was spearheaded by Evan Jones, who nearly succeeded, but was hampered by a slump in the slate industry and the onset of the First World War, when the quarry was "non-essential" and was mothballed. It reopened in 1919, but was in a poor financial position, and was bought by members of the Colman family, better known for producing mustard. They kept it running until 1930, but failed to find markets for the finished product. It was mothballed until 1947, when it was sold, but new plans to reopen it failed, and the pumps were turned off in 1948, after scrapmen had removed much of the machinery. Of the five slate veins in the region of Blaenau Ffestiniog, most of Rhosydd's output was extracted from the Old Vein. The workings started at the West Twll, where the rock outcropped, but the quarry soon developed into underground workings. A series of adits were constructed, to provide access as the mine got deeper, with the lowest at level 9. Trucks moved along this adit by attaching them to an endless chain, driven by a waterwheel. The mine eventually reached level 14, with rock raised by an internal incline to the level 9 adit. At its peak the quarry was one of the largest underground workings outside of Blaenau Ffestiniog, with 170 chambers.

Moel Druman is a mountain in Snowdonia, North Wales and forms part of the Moelwynion. It is a subsidiary summit of Allt-fawr.