Overview
The one stretch of the Glencullen River worth going out of your way for is the section through Knocksink Wood, just north of Enniskerry. The wood is a nature reserve and Special Area of Conservation, best known for its “petrifying” springs, seeps so rich in lime that they slowly coat moss, twigs and leaves in a stony crust of tufa. That, and the stands of old sessile oak, are the reason to come.
The river itself is an 11-kilometre watercourse (Abhainn Ghleann Cuilinn, the holly glen) rising at about 442 metres on the slopes of Glendoo, opposite Tibradden, on the border between southern County Dublin and northern County Wicklow. Below Enniskerry it’s also called the Cookstown River (An Chlóideach) before it joins the River Dargle near Bray. The valley follows a geological fault: Devonian granite to the north-west, Ordovician schist to the south-east, with the river cutting down through glacial till and gravels. Some of the granite quarried around Glencullen went into Dublin’s General Post Office.
Walking Knocksink Wood
Knocksink has up to 11km of trails, on firm but unpaved surfaces, following the river through the reserve. Stick to the marked paths, both to protect the fragile tufa deposits and because the woodland floor is a habitat in its own right, with rare plants like blue fleabane, ivy-leaved bellflower and yellow archangel among the ferns. The best of the wildflowers is spring and early summer.
Access is off the Dublin (Monastery) Road, where there’s parking at the reserve gate. There are no toilets, café or staffed visitor facilities on site, so pick those up in Enniskerry a short walk away.
Fishing and wildlife
The river is a reliable brown trout water, clearest and fastest in the upper and middle reaches, with a modest run of salmon and a population of eels closer to the Dargle. Its ecological status for fish was rated “good” in 2018. Inland Fisheries Ireland manages the water and you need a valid IFI licence to fish it.
The water runs cold and fast, which rules out swimming but makes the banks a good spot to sit and watch. Early spring and autumn bring the most bird movement through the valley.
Practical information
- Access – the river and woods are free to walk. The trailhead and car park are off the Dublin (Monastery) Road, just north of Enniskerry.
- Hours – the reserve has no gates; visit in daylight and keep to the paths.
- Getting there – by car via the R116 from Sandyford or from Bray. Public transport is limited: buses serve Enniskerry, and Bray has the nearest rail station, followed by a taxi or walk.
- What to bring – sturdy footwear; the unpaved paths get slippery after rain, and the riverbank is no place to be careless with children.
Nearby
Enniskerry has cafés, shops and a weekly market, and makes the natural base for a day here. Glencullen Adventure Park, up the valley, has mountain-biking and walking trails, and Johnnie Fox’s in Glencullen village is one of the country’s better-known old pubs for a meal after a walk. For more river walking, the Avonmore River and Meeting of Waters is a short drive south into the Wicklow Mountains.