The walk starts by Cow Green Reservoir, which was formed in 1970 by the building of a dam across the River Tees. The dam was built after fierce opposition since the reservoir flooded a large area of botanical importance.

The nature trail leads for a mile along the east side of the reservoir to Cow Green Dam, where the River Tees emerges again from the dam wall, and starts its descent to Cauldron Snout waterfall.

The river now plunges in a forming cataract, and a series of steep cascades, to the peaceful meadows 60 metres below. The best view of the waterfall is from these meadows, where the river quietly flows past the crags of Falcon Clints. Another fine view is from the ridge between the Tees and Maizebeck on the other side of the river.

The high altitude of the region means that the average temperature is cool, similar to that of Reykjavik in Iceland. This is one of the factors which has made Upper Teesdale a nature reserve of world importance. A range of Arctic and Alpine plants have remained here since the ice sheets of the last glaciation receded some 15,000 to 20,000 years ago.

There are many rare plants which are very fragile, so visitors must keep to the paths. The small, hardy Swaledale sheep play an essential part in maintaining the botanical balance by grazing, which prevents coarser grasses from spreading over the rarer species.

The grassy limestone areas contain many different plants and grasses. There are common varieties such as harebell, wild thyme and rock rose, and many rare species such as the spring gentian, which is only found in this spot and in south west Ireland.

The limestone grasslands are separated by heather and cottongrass areas, which grown in peat. Many upland birds nest here, such as Red Grouse, Golden Plover, Red Shank, Lapwing, Curlew, Wheatear, Skylark and Meadow Pipit.