One of those must-do hikes. Hafren Forest is home to the source of the River Severn — Britain's longest river — and this strenuous trail follows it from a tangle of waterfalls and boardwalks up through ancient forest and onto open boggy moorland, all the way to the source itself on the slopes of Pumlumon.
6.3
Miles
248m
Ascent
317–418m
Elevation
~5 hrs
Time
Oct '25
Completed
SY18 6PT
Postcode
⚠️ Before you go — read this There is limited or no mobile signal in Hafren Forest. Download your route to your phone or GPS device before you set off. This is an isolated trail — go well prepared with layers, waterproofs, food and water. The car park fills up fast — arrive early, especially in peak season and autumn. Take the scenic route past Llyn Clywedog on the way out to ease congestion on the narrow lanes.

Getting There & The Drive In

Hafren Forest is about 6 miles west of Llanidloes. Depending which way you approach the main car park (Rhyd-y-benwch), the drive through the mountains can be quite spectacular. If you come via the Llyn Clywedog reservoir road, you'll pass a stunning lake — a real bonus for fly fishermen and anyone who appreciates dramatic Welsh scenery.

Parking is free at Rhyd-y-benwch. There are also temporary toilets in the car park and a picnic area nearby. The trail is waymarked from the car park — look for the information panel at the start which shows all four route options.

The Trail — Source of the Severn

We completed the Source of the Severn Trail in October 2025 — and what a time of year to do it. The autumn colours in the forest were absolutely spectacular, with russet bracken, golden birch and deep green spruce all side by side. The air was fresh and the river was running well.

"It's a hard-going trail in places — be prepared. But there are plenty of places to stop along the way, and the isolation is part of the appeal."

The trail sets out on a well-surfaced path following the infant River Severn (Afon Hafren) upstream alongside the water and through the forest. Early on you pass the boardwalk sections — genuinely lovely, winding through the forest with the river rushing alongside. The cascades and waterfalls in this lower section are superb, especially after any rainfall.

Beyond Blaen Hafren Falls the route climbs steeply to the forest boundary. Here it opens out onto stone slabs and a loose stone path through open boggy moorland — a completely different world from the forest below. There may be sheep on this section, and the views back down across the forest and towards the distant hills are impressive. The source itself is marked by a carved wooden post in a peat bog on the slopes of Pumlumon — a genuinely moving moment to stand at the beginning of Britain's longest river.

The return is via forest road and a narrow loose shale path back alongside the river. There are several benches along the route and information panels to help you track your position.

The Four Trails at Hafren

♿ Cascades Walk
Accessible · 0.6 miles · 30 mins
Boardwalk to a viewing platform over the cascades
🟡 Severn-Break-its-Neck Trail
Moderate · 1.4 miles · 1 hour
Riverside path to the famous waterfall and back
🟡 Blaen Hafren Falls Trail
Moderate · 3.8 miles · 1.5 hours
Through the heart of the forest to Blaen Hafren Falls
🔴 Source of the Severn Trail ★
Strenuous · 8.1 miles / 6.3 mi GPS · ~5 hours
The full route to the very source of the River Severn

Wildlife — Keep Your Eyes Peeled

Wildlife is a real highlight here. Ospreys nest near Llyn Clywedog reservoir — if you're visiting between March and August there's a live camera feed on YouTube (search "Llyn Clywedog Ospreys"). There's also red kite activity in the area, and the forest and river corridor supports a rich range of birds and mammals. Look out for dippers on the river rocks, siskins in the conifer canopy, and red squirrels have been recorded in parts of the forest too. We saw plenty of wildlife on the walk — the October quiet helps enormously.

History Along the Route

📜 Hafren Forest & the River Severn Planted by the Forestry Commission in the 1930s, Hafren Forest takes its name from Afon Hafren — the Welsh name for the River Severn. The river rises in a peat bog on the slopes of Pumlumon (Plynlimon), Mid Wales' highest mountain. At 354 km (220 miles), the Severn is Britain's longest river, flowing through Shrewsbury, Worcester and Gloucester before reaching the Bristol Channel. The trail passes several heritage features: a standing stone, remains of an old mine, and a farmstead — look for the interpretation panels along the route. Hafren Forest is also the official start point for both the Wye Valley Walk (136 miles to Chepstow) and the Severn Way (210 miles to Bristol).

Practical Information

🚗 Parking: Rhyd-y-benwch car park — free. Gets busy fast. Arrive early.

📍 Postcode: SY18 6PT (covers a wide area — follow signs, not just satnav)
🗺️ OS Grid: SN 857 869 (Explorer Map 214)

📶 Signal: Limited or none — download your route before arrival

🚌 Public Transport: Nearest mainline station: Caersws. Check Traveline Cymru for bus connections.

🌐 More info: Natural Resources Wales — Hafren Forest

📷 Photos from the Walk