The Aeron rises in Llyn Eiddwen, a quiet lake in the hills called Mynydd Bach, and then runs west and northwest for about twenty-five miles before reaching the sea. The valley it carves is broad and shallow - this is not a dramatic gorge but a gentle, fertile cleft through softly contoured Welsh farm country. The tributaries have names that read like a roll-call of Welsh hill streams: Gwenffrwd, Nant Wysg, Nant Picadilly, Nant y Wernen, Nant Rhiw Afallan. The Afon Mydr brings in water from old woodlands and dairy farms above. Below the source the river slips past the villages of Talsarn, Felinfach, Ystrad Aeron and Ciliau Aeron, each set in its own little fold of green. Eight mansions were built along this valley in the 18th and 19th centuries - more than the modest size of the river would normally support - and that density of country houses is the surest possible signal that the land was rich.

Before it reaches Aberaeron, the river runs close to Llanerchaeron, an 18th-century country estate now owned and beautifully restored by the National Trust. A footpath threads along the bank between the estate and the harbour town - one of the best short river walks in Ceredigion, signposted as the Aeron Valley Trail, ending where the freshwater meets the salt at the inner basin of Aberaeron harbour. The river is not large; you can step across the upper reaches in places. But it sustains a population of salmon and brown trout, and there is something quietly remarkable about a river that has been polluted, recovered, and continues to support migratory fish despite agricultural runoff and the legacy of creamery effluent that nearly killed it in the 1970s.

From 1941 to 1943, before he and Caitlin moved north to New Quay, Dylan Thomas lived in a secluded mansion called Plas Gelli just outside Talsarn. He came back to the Aeron valley repeatedly in letters, in radio broadcasts, in scraps and notes. His 1949 piece Living in Wales mentions 'the peacefulness of the Aeron valley.' The Dylan Thomas Trail now runs the river's length from Talsarn through Ystrad Aeron and Ciliau Aeron down to Aberaeron, marked by blue plaques and information boards opened by Aeronwy Thomas herself in July 2003. The Rev Eli Jenkins' Pub Walk - named for a character in Under Milk Wood - follows the small Afon Dewi to the sea, passing the farm of the Cilie poets near the river's mouth. Thomas was not the only writer the Aeron drew. T.S. Eliot holidayed through the 1930s at Ty Glyn in Ciliau Aeron, after the publisher Geoffrey Faber bought the house in 1930. James Hughes, the dockworker-poet known as Iago Trichrug, was born in Ciliau Aeron in 1779. The Aeron valley has been making poets for as long as records exist.

Talsarn and the upper Aeron supported a tradition of country poets - beirdd y wlad - through most of the 19th century. John Davies, born in 1722, kept a diary of poems from 1796 until his death in 1799; it sits today in the National Library of Wales. John Jenkins and his brother Joseph were active in the mid-1800s; Joseph wrote for agricultural journals and a book about his travels in Australia, which is unusual material for a Welsh-speaking farmer-poet. Stevie Krayer, who lived in Ciliau Aeron for more than twenty years, has more recently written a sequence of poems about the Aeron itself. So the river goes on collecting writers the way it collects tributaries, drawing them in from the hills and carrying them slowly down to the sea.