The town takes its name from a 7th-century monk, Saint Collen, who is said to have arrived at the riverbank by coracle and founded a church beside the Dee. The church that bears his name is the only one in Wales dedicated to him; he may have had connections with Colan in Cornwall and Langolen in Brittany, suggesting a Celtic religious circuit of which Llangollen was one stop. The bridge across the Dee is older than almost everything else: a 14th-century structure built around 1345 by John Trevor, later Bishop of St Asaph, replacing an even earlier bridge from the reign of Henry I. The current bridge, much rebuilt and widened in the 16th, 19th and 20th centuries, is a Grade I listed structure and a Scheduled Ancient Monument. An anonymous old rhyme counts it as one of the Seven Wonders of Wales.

On a hillside above the town stands Plas Newydd, a black-and-white timbered house with carved-oak interiors and a sloping lawn. From 1780 it was home to the Honourable Sarah Ponsonby and Lady Eleanor Butler, two women from prominent Anglo-Irish families who eloped together to escape arranged marriages and live as a couple. Their household, including their maid Mary Carryl, lasted nearly fifty years. They received visitors from across literary and political Europe - Wordsworth, Shelley, Byron, Walter Scott, the Duke of Wellington - and refused to leave. When they died they were buried in St Collen's churchyard with Mary Carryl, all three sharing a single memorial. Their relationship was never publicly named in their lifetimes, but their household was widely understood, and they have come to be claimed as foundational figures in lesbian history. The house is now a public museum.

Above the town to the north, on a steep limestone hill, stand the ruins of Castell Dinas Bran - a 13th-century fortress built by the Princes of Powys Fadog. The walk up is steep and the view from the top runs in every direction: the Dee valley to the south and west, the Eglwyseg Rocks to the north, and the slow Carboniferous limestone escarpments fading toward Wrexham. Beyond the castle, the single-track Panorama Walk follows the contour line below the escarpment. A monument to the Welsh poet I.D. Hooson sits near its eastern end. Higher up still, on the moor, the Pillar of Eliseg - a stone cross-shaft erected in the 9th century - records the genealogy of the kings of Powys. Valle Crucis Abbey, founded around 1201 under the patronage of Madog ap Gruffydd Maelor, lies down in the valley below.

The International Musical Eisteddfod started in 1947. It is not the same thing as the National Eisteddfod of Wales (which Llangollen hosted in 1908, visited that year by Lloyd George and Winston Churchill). The International is a music festival in the strict sense - choirs, folk dancers, soloists and instrumentalists competing in categories from across the world. Pavarotti competed as part of the Corale Rossini in 1955, winning the choral competition - an experience he later described as the most important of his musical life, and the one that decided him on becoming a professional singer. He returned in 1995 to give a sold-out solo concert. The festival opens each year with a costumed parade through town led by the Llangollen Silver Band, and ends six days later. Crowds, choirs and accents fill the streets. Then it ends, and the town goes back to being a market town on a river.

Three different transport ages meet at Llangollen. The 14th-century bridge crosses the Dee just upstream of the rapids where, today, slalom kayakers and canoeists compete in international championships. A short walk away is Llangollen Wharf, where horse-drawn excursion boats still pull tourists along the navigable end of the Llangollen Canal toward Horseshoe Falls. The canal's main purpose was never freight - it has been a water-supply channel for over a century, drawing Dee water for Crewe and Nantwich - but it has become one of Britain's most-cruised inland waterways. The Pontcysyllte Aqueduct, five miles east, is now a UNESCO World Heritage Site. And the heritage Llangollen Railway runs west up the valley toward Corwen, eleven miles of restored line on a route that closed under Beeching in 1965. Three industrial centuries, all still moving, all running through one small Welsh town.