The Lefel Fawr at Pontrhydygroes driven under the B4343 is the longest draining adit in Mid-Wales. The portal is under the road in a high wall - the least expected place for it to be. The adit drained Logaulas, Penygust, Glog Fach and Glog Fach mines.
The water from the 360 fathom level over 780 feet deep at places, runs through a field and to a newly reinstalled water wheel by the Welsh Mines Preservation trust. It stands impressively above the lane to Tynygraig and an information board nearby.
Down in the ravine below the spectacular miner's bridge crosses the Ystwyth and the tips from lefel fawr can be seen and the waterfall from it. At the bottom of the waterfall note a double-flanged wheel.