Gardens: Sir William Keswick's Glenkiln estate

There are three things of which prospective visitors to Glenkiln, Sir William Keswick's extraordinary collection of 20th century sculpture in south-west Dum-friesshire, should be aware. The first is that the collection is located in a strikingly beautiful and remote part of rural land, where fields of sheep and cattle meld into moorland. Second, it is a very hard place to find. Third, you need to be prepared to walk on rough terrain in all kinds of weather.

But negotiating the single-track road that winds through the wild landscape west of the village of Shawhead and coping with a lack of road signs is part of the fun. By the time a Henry Moore sculpture appears on the horizon, mercifully close to the road this one, you feel a thrilling sense of discovery. And this is just the beginning; the beauty of Glenkiln is that you are free to explore and discover the works at your own pace. There are no signs, and you happen upon the sculptures by surprise or find them hidden among groups of trees or behind shrubs.

Assembled between 1951 and 1976 by Sir William Keswick, who spent much of his working life in Hong Kong, the collection includes work by artists such as Rodin, Moore and Epstein. Taking advantage of the dramatic beauty of his family estate six miles west of Dumfries, Sir William worked closely with the artists, experimenting with the novel idea of placing their works in an open, natural setting. The first of its kind, this collection later served as an inspiration for other sculpture gardens such as Iain Hamilton Finlay's Little Sparta.

Sir William's close friendship with Moore resulted in the commission of works, creating a unique opportunity for the artist to experiment with placing his work in open land. Moore's Standing Figure, a massive bronze raised up on a rock overlooking a field of sheep, is easily found if you turn immediately left after the humpback bridge at Glenkiln. A controversial piece, once mistaken for a tractor spare part, it is surprising to find it in such a remote setting, something best appreciated once you understand the advantage of being able to wander round the piece and see it from all angles.

The sculptures also change according to the weather. A piece that stands out during a moment of bright sunlight can disappear into the side of the hill when the weather changes, which it does rapidly, especially in winter.

A few hundred yards further up the road a newly constructed bridge over a ditch leads to a narrow metal gate. Climb the hill and you will find a simple memorial celebrating Sir William and Lady Keswick's diamond wedding – or "splicing". In strong contrast to the dramatic figures elsewhere on the estate, this stone memorial is a moving reminder of the man behind this collection and that this is an intensely personal place.

Higher up, and further east, a view down over the Glenkiln reservoir appears over the shoulder of the hill. From here you can just make out the site of the tiny car park that marks the official start of a tour. This can be reached by walking or by road along the side of the reservoir. Once you are there the scene is set by the French sculptor August Rodin's larger-than-life bronze figure of John the Baptist. The sight of a piece by the legendary artist in the wilds of south-west Scotland delivers a powerful surprise even when expected.

Turn left out of the car park and walk or drive for about half a mile to a short track on the right. This leads up the side of the hill towards Moore's quirky King and Queen. Commissioned in celebration of the Queen's coronation in 1953, the bronze statue stands out clearly when backlit by the low winter sun, but darkens rapidly when the light changes. Higher still is Moore's 11ft Glenkiln Cross engraved with themes taken from Mexican and Mayan art. Its imposing outline can be seen from several locations and serves as a focal or orientation point.

From here the track leads to the end of the field. Go through the gate and stay on the track until you pass a wood on the right. Here, hidden in a small copse of Scots Pine stands the lonely, shadowy figure of a woman. This is Jacob Epstein's Visitation, a representation of the Virgin Mary announcing her pregnancy to her cousin Elizabeth, mother of John the Baptist. Originally intended as one of a pair, the figure highlights the vulnerability of Mary's situation.

The sheer drama and variety of the artworks at Glenkiln coupled with a sense of discovery when stumbling across a work for the first time makes a visit quite an experience – not forgetting the physical exercise – a full tour is about five miles long and takes at least two hours, even if you find everything first time. The audacity of this unique garden leaves a lasting impression, heightened by the fact that it is relatively unknown. We are fortunate to have such a place in Scotland.

Glenkiln Estate Sculpture Garden, Shawhead, Dumfries and Galloway, DG2 9UE. Glenkiln Estate is located near Shawhead. Drive west from Dumfries on the A75 for 6 miles to the Shawhead signpost. Turn right into village. Turn right, then left and follow signs for Glenkiln. Open all year, www.snipurl.com/glenkiln

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• This article was first published in The Scotsman on Saturday 09 January, 2010.