Devil's Appendix

The Devil's Appendix (Nant Clogwyn y Geifr) is the tallest single-drop waterfall in Wales and one of the tallest in the United Kingdom. It is a plunge style waterfall located on the Clogwyn y Geifr cliffs beside Twll Du in Cwm Idwal, Snowdonia, Wales.

It is formed where a small stream falls for approximately 305 ft to reach the slopes above Llyn Idwal. Depending on flow and the ambient temperature, it can be either an ice climbing route, a single drop waterfall, or a broken waterfall.