The Afon Mynach is a small river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 in Ceredigion

Ceredigion

Ceredigion is a county and former kingdom in mid-west Wales. As Cardiganshire , it was created in 1282, and was reconstituted as a county under that name in 1996, reverting to Ceredigion a day later...

, Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

.

Its source is at the meeting of two smaller rivers, the Nant Rhuddnant and the Afon Merin. Both of these streams have their sources in lake

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

s high on the Cambrian Mountains

Cambrian Mountains

The Cambrian Mountains are a series of mountain ranges in Wales, reaching from, and including, the South Wales mountains of the Brecon Beacons, north Carmarthenshire and Ceredigion, the Black Mountains of eastern Wales, to Snowdonia in North Wales...

, the Afon Merin flows from Llynoedd Ieuan, and the Nant Rhuddnant from Llyn Rhuddnant.

The Afon Mynach is notable for the famous Mynach Falls

Mynach Falls

Mynach Falls is a waterfall near Aberystwyth in the county of Ceredigion, Wales.It occurs where the River Mynach drops in 5 steps down a steep and narrow ravine before it meets the River Rheidol....

 in the village of Devil's Bridge

Devil's Bridge, Ceredigion

Devil's Bridge is a village in Ceredigion, Wales.- Description :The bridge spans the Mynach, a tributary of the Rheidol. The bridge is unusual in that three separate bridges are coexistent, each one built upon the previous bridge...

 (Pontarfynach), where the river plunges 90 metres into the gorge of the River Rheidol. It is also famous for the three bridges built one on top of the other in the same village, the lowest of the three said to be built by the devil (hence the name Devil's Bridge), but most probably built by the monks of Strata Florida.