The viaduct crosses the valley of the River Eglwyseg at Pentrefelin. It carried the horse tramway designed by Henry Dennis for John Taylor & Son, and constructed in 1852 to carry slate from the Upper Cambrian slate quarries at Clogau, at Oernant (Maesyruchan) and Moel-y-faen to their Llangollen Slab and Slate Works and wharf on Llangollen Branch of the Ellesmere (Shropshire Union) Canal near Pentrefelin Bridge, a distance of 4.5 miles (2.8km).

The viaduct comprises of a rubble stone revetted embankment approximately 130m long. A central wider arch spans the river Eglwyseg with a narrower flood arch on either side. All arches have rusticated and margin dressed stone quoins and voussoirs with slightly emphasised key stones. The arches are flanked by pilaster buttresses and on the south side there are 7 large raking buttresses, perhaps a later addition (Cadw listing).

This is a well preserved example of a horse tramway viaduct, and of significance as a relic of the slate extraction industry which once formed a major part of the economic life of the Llangollen district.

RCAHMW, 4th September 2008

Sources
Edwards I, `Slate Quarries in the Llangollen District?, Denbighshire Historical Society Transactions 324, 1985, pp 91-120
Hubbard E, Clwyd, Buildings of Wales series, 1986, pp223-4