Initially the trail climbs fairly steadily across heathland. It undulates gently and whilst these are good for trail drainage the ups and downs make getting into a rhythm tricky. What goes up must come down and shortly after you begin a fun singletrack descent which drops out next to the toll-booth at the start of the Forest Drive. Make the most of that singletrack descent because the next 5 kilometres of the trail are uphill.

The foot of the climb lies just across the forest road next to the stream. The stream nestles in a steep little valley and the trail clings precariously to the sides only dipping briefly to cross from one side to the next over slippery wooden bridges where the valley sides are too steep to build on.

The trail winds back and forth via a number of tight switchbacks - here at MTB-Wales.com we're big fans of switchbacks but several of these have been built just a little too small for mere mortals to ride. Either that or the trail builders have very short bikes - maybe these trails are built by pixies after all.

The Forest Drive is crossed a couple more times in the same way: climb steeply to the road, cross over it, climb steeply away, emerge onto next section of road. Eventually the trail climbs on an old forest road and the climbing is over - for now. On the left lies the first section of downhill singletrack. It's nothing too steep, but meanders across a felled section in between the tree stumps. A long straight section then drops down alongside the Forest Drive. The trail soon turns away from the road and climbs through the trees. Here the trail is fun - the climbing is easier even if the surface is slippier.

A rollercoaster section leads into a fast, bumpy descent that is spoilt at the bottom by a brutal and barelly rideable 90 degree left-hander. Initially this was unsurfaced and tricky to climb but it's been concreted to provide traction. The push over the top is short and leads into one of the sweetest sections of singletrack in Wales.

Clinging to the hillside the singletrack is barely more than a metre wide as it snakes along. Of course it's not all downhill, this is Cwmcarn after all, but the inevitable uphill section comes as quite a relief after the constant darting left and right around the numerous little obstacles that the trail throws up at you.

A short section of doubletrack and then the darkness of the forest beckons once again for another weaving section through the trees. And then, suddenly, you're out in the open on an old forest road. The singletrack appears to climb slightly ahead of you and then descends. Then it narrows, narrows and narrows some more.

As your speed increases you become steadily less aware of the large degree of exposure on your left hand side. Far below people go about their daily business in a South Wales valley whilst you shoot along the hillside darting around rocks and trees stumps.

After what seems like ages trees approach once again and a short section of singletrack beckons you into the relative safety of a small coppice. Just as you lower your guard, the end of the singletrack throws up a cruel surprise - a series of staggered rocks, designed to slow riders as they emerge on to the forest road.

A short forest road section and then the trail builders have the last laugh - a descent back to the car park so fast that you feel like you're parachuting in. And then it's all over.

The Cwmcarn trail is short at 13.5 kilometres and there's a lot of climbing and the first real climb lasts for nearly 6 kilometres ! But once you do gain the height the payback is excellent in the form of a number of grin-inducing singletrack descents.

The trail will certainly appeal to a lot of people but this is definately not a beginners trail. The shear amount of climbing and the technical challenge that this offers will put off all but the most determined of beginners.

But for the experienced rider Cwmcarn offers a wealth of delights. After wet weather it is slippery making the trail particularly technical if not very sustainable. The singletrack climbs are demanding, and the descents require absolute concentration.

Fans of more natural trails will love Cwmcarn because virtually the whole trail is unsurfaced. This makes the surface very slippery in wet weather and we suspect that some of the singletrack will take a while to dry out after heavy rain. Here at MTB-Wales.com we are not fans of semi-slick tyres at the best of times and Cwmcarn is the last place on earth that we would choose to use them. Stick with some good knobblies and you'll be fine.