Substantial underground workings. Remains of mill with some machinery. Rhiwbach tramway incline opposite.**

Very little of Maenofferen remains accessible to the public today, as the underground workings on two levels are closed to visitors. These workings are historically significant for containing the last operational underground inclines in the slate industry, which incorporated original brine-bath speed regulators. The mill area has been largely cleared, though the empty shell of the main mill building survives, revealing modifications made when the projecting waterwheel was removed and the roof required repair.

Several structural remains document the quarry’s technical history. A distinctive kinked flue survives from an old engine house, and on the long-abandoned David Jones section stands a machine-bored adit, evidence of an unsuccessful 1870s experimental trial with a Hunter twin-head boring machine. A cut-and-cover tramway tunnel survives, which once conducted slate to tipping areas on the old Votty site.

The incline systems that connected the underground workings to the surface remain partially preserved. No. 2 incline and its remote drum house survive but are in poor condition, though below it sits a good rail formation and bridge dating from the Votty underground workings. The tramway route across Bowydd property leading to No. 1 incline remains traceable across the landscape. No. 1 incline is intact and features a compact drum house set into the rock. No. 3 incline climbs to the level of the Rhiwbach Tramway and retains a fine drum house. Along the first section of this tramway runs a notable slate-lined and slate-covered leat with a piped feed to the former power station. Various winders and other artefacts remain scattered across the site, and the old Hysfa workings to the north remain open.

Maenofferen quarry opened in the early 1800s but remained unprofitable until Greaves took it over in the 1850s. From the mid-19th century onwards, it developed into a major entirely underground quarry positioned at over 1,300 feet elevation. By the 1890s, the operation had grown substantially, producing over 14,000 tons annually and employing more than 400 men. Two water-powered mills processed the extracted slate, each containing approximately 50 saws and 50 trimmers. Locomotive haulage was extensively deployed on site to move materials, and the underground trunk incline operated as a balanced system before later electrification.

The introduction of electricity in the 1890s represented a transformative development, significantly improving both power generation and haulage capabilities. A dedicated hydroelectric station built in 1918 proved so effective that it remained operational until the 1980s. The quarry became an innovator in extraction technology, pioneering the use of wire saws in underground slate extraction. Greaves reacquired Maenofferen in the 1970s and invested in rebuilding the mill, enabling the quarry to operate as the last fully underground quarry remaining in the district.

Transport and logistics evolved considerably throughout the quarry’s operation. Early operations relied on the Diffwys incline until the Rhiwbach Tramway was constructed through the site. The quarry initially used the Nos. 1 and 2 Rhiwbach inclines until 1920, when it constructed a new incline via Votty and Bowydd to circumvent high transport charges. This situation reversed in 1928 when Maenofferen acquired Rhiwbach quarry and reverted to using the Rhiwbach line for transport. After World War II, some traffic from the quarry used No. 1 incline to reach the mainline railway, though until 1976, the majority of slate departed by lorry from the foot of No. 2 incline. The completion of a new road in 1976 rendered No. 2 incline redundant.

Cadw have been doing some work on the roof and supports of the main mill. Roofs on the workshops are in poor and dangerous condition. The roadway up from Votty is periodically affected by inwash and landslides.