This is a challenging and very scenic high circle along a spectacular ridge in the Black Mountains, which is the Easterly side of the Brecon Beacons National Park. Visit Waun Fach, the highest point, and also Castell Dinas, the highest Norman fort in Wales. Its about seven miles, about 4.25 hours walking. Use the map OS OL 13, Brecon Beacons, Eastern, grid ref: 175 296.

Park at the Castle Inn, Pengenffordd, between Talgarth and Crickhowell on the A479. It's very easy to reach. £1 parking all day. A great place for refreshment when you have finished. The pub is also on the bus route X12.

T his strenuous but stupendous circle is for those who are fit and would like a challenge on a clear, sunny day. It explores a horseshoe-shaped ridge in the Black Mountains, near Talgarth.

Visit Castell Dinas, the highest Norman fort in the country and go up via Y Grib to Waun Fach, the highest point in the Black Mountains.

There are panoramic views nearly all the way and walking is practically all in the open.

It's a walk best done on a clear sunny day and when there hasn't been much rain as it will be very boggy and peaty on top and quite difficult to negotiate.

Go well prepared for changeable weather and winds. As a precaution on a high-level walk like this, let someone know where you are going and what time you leave.

START

Drop down from the back of the car park on to a track below following the footpath sign to Castell Dinas. Turn right. Not far on, cross left over a stile and go ahead in the field following the left fence. Ahead is the range you will be walking.

Cross a stile and stream and continue on. Go over another stile and climb quite steeply. Cross a stile on your left and maintain direction and continue to climb. There are good views as you go, so take your time and enjoy them. Cross a stile and follow the arrow up,

1. CASTELL DINAS

Bend left on a grassy track and come to just below the old keep of Castell Dinas with a ruined wall ahead of you.

Castell Dinas is a former Iron Age hill fort and Norman castle at a height of 450m – probably the highest castle site in the country. Certainly the views are spectacular. It sits as a kind of detached hill on the Y Grib ridge you are about to tackle.

Continue on, dropping downhill, cross a stile and then follow the permissive grassy track up steeply starting along the ridge.

The path passes just below a high point and then continues on. Pass a stone cairn.

2. CAIRN

According to tradition, you should add a stone to the cairn as you pass. Carry on up and eventually come to a rocky outcrop – a fine place for a rest and to soak up the panorama.

After another steep climb reach a tall cairn, which you will have seen from a distance and looks rather human shaped with a small head. This is Y Grib.

3. Y GRIB

It's still in the same direction. Ahead of you is a long broad ridge with Pen y Manllwyn as a rather indistinguishable summit on the right of it. The ridge is your next goal. So continue on for a while.

4. PATH

Don't go left along the track below the ridge. Instead, take another fairly well-worn path which heads straight on up to the ridge – again it is a steep climb.

Turn right along the ridge and continue to the cairn on Pen y Manllwyn.

5. PEN Y MANLLWYN

Head along the plateau, still climbing, and negotiating what can be a very peaty and boggy path in places, badly eroded over the centuries by the weather and walkers.

There's a section of flat walking when you can enjoy the views to the full and then a steeper climb to the summit of Waun Fach.

6. WAUN FACH

This is the highest point in the Black Mountains at 811m and sadly, the summit is very uninspiring with a large, crumbling stone plinth sitting in an island of bare, boggy peat. But the air and the views are tremendous.

From here, turn sharp right (more than 90 degrees) and head off along the ridge of Pen Trumau to another summit, or col. You are turning down the final side of the horseshoe.

Again, it will be boggy along here and difficult underfoot after a period of rain.

Continue all the way to the end. Now it's downhill, so follow the ascending path on down.

7. CROSSING

At crossing tracks, turn very sharp right (more than 90 degrees) dropping down under the ridge you have been on. Stay on the main track at a fork – it's the left-hand path. Follow this down through huge swathes of whimberries until you reach a farm track. Follow this all the way down, through gates, and on as it becomes a sunken thoroughfare.

8. LANE

Eventually reach a lane and turn right. Follow it around a bend, ignoring a turn.

9. CWMFFOREST

Come to the farming hamlet of Cwmfforest, pass a riding centre and bend with the lane uphill. At a sharp left bend, go straight on along a track.

Stay with this for about half a mile, ignoring a left turn, all the way back to where you started and turn up left to the car park.

The Castle Inn, Pengenffordd, Nr Talgarth, Powys LD3 0EP. Tel: 01874 711353; website: www.thecastleinn.co.uk. Please call before setting out to confirm opening times.