Overview
Prince William’s Seat and its neighbour Knocknagun are both about 555 metres (1,821ft), separated by a shallow col on the northern rim of the Glencree valley, right on the boundary between County Wicklow and County Dublin. Both lie in the Wicklow Mountains area. The higher slopes are exposed, and in clear weather there are views north towards Dublin Bay and the coastal headlands.
The walk
The Wicklow Way, Ireland’s first waymarked long-distance trail, crosses hills and woodland in this area. Use the official map for a waymarked walk, and check route and access before leaving the signed trail. Dogs are not allowed on the Wicklow Way, so leave them at home. This page does not describe a standard loop to the summit, so plan your own route from the official map and do not assume a route is open to the public just because it is visible on the hillside.
The open hill above the forest is heather-covered and the ground can be boggy and rocky near the saddle between Prince William’s Seat and Knocknagun. Carry navigation equipment, turn back if conditions deteriorate, and do not leave the waymarked trail without checking access.
The summit carries a concrete triangulation pillar, likely a relic of the 1960s retriangulation of Ireland rather than the original 1830s survey. On a clear day the views from the hill take in:
- the conical Great and Little Sugar Loaf and Bray Head to the east
- the Dublin city skyline and the sweep of Dublin Bay
- the higher Wicklow peaks, including Kippure and the Tonduffs, to the south
- the far horizon of the Irish Sea
History and naming
The royal name is usually put down to Prince William, brother of King George IV, after a visit to Ireland in 1821. But placename research by the Irish academic Paul Tempan suggests it may have been assigned later by Ordnance Survey surveyors in the 1830s, possibly muddled with a neighbouring landmark.
Just over a kilometre west sits Knocknagun (Irish: Cnoc na gCon, ‘hill of the hounds’). Near its summit stands a great granite tor known locally as Fitzwilliam’s Seat, a resting place for the hunting parties of the Fitzwilliam family, who owned the surrounding land from the mid-16th to the late-17th century, and a name still recorded in the area in 1939. Some historians reckon the surveyors swapped ‘Fitzwilliam’ for ‘Prince William’ when they mapped the adjacent, slightly sharper peak. The mountain sits in the townland of Glencullen Mountain (Sliabh Ghleann Cuilinn), a reminder of a landscape shaped by both aristocratic estates and centuries of hill farming.
Through the seasons
The mountain changes noticeably with the year. Spring brings pink foxgloves and purple heather across the upper slopes, while early summer adds bilberry and gorse, whose yellow flowers carry a faint coconut scent. Autumn turns the bracken and heather russet and gold. Winter walks are possible, but the exposed summit ridge can be icy and the boggy saddle between the two peaks turns treacherous in a freeze.
Practical information
- Trail and access: use the official Wicklow Way trail information and the waymarks. Check route and access before leaving the signed trail.
- Dogs: not permitted on the Wicklow Way. Leave dogs at home.
- Public transport: there is no realistic public transport to the hills here, so most visitors come by car. Check parking arrangements and any signage before you go.
- Accessibility and terrain: uneven ground, rocky sections and moderate gradients mean it is not suitable for wheelchairs, pushchairs or standard strollers. Hiking boots with good grip are essential, especially after rain when the grass and the saddle near Knocknagun turn slick and boggy.
- Navigation: carry a map or a downloaded GPX file, as visibility can drop quickly in mist.
- Facilities: there are no toilets, cafés or shelters on the summit. Bring water, food and a waterproof layer.
- Nearby: Powerscourt Estate and Powerscourt Waterfall are a short drive away, and Glencullen village has Johnny Fox’s, which bills itself as one of the highest pubs in Ireland.
Pick a clear day. In mist the summit is just a concrete pillar in grey soup, and the Dublin Bay view that makes the climb worth it disappears entirely.