It's surprising what you find when you know where to look. Or maybe know how to look.

Abby Hunt plucks a loose piece of stone from the top of a typical drystone wall running close to one of Britain's most wondrous sights, Rievaulx Abbey.

Although not dissimilar in colour to the rest of the wall material, closer inspection reveals that this is a not stone at all. It's a lump of slag. By lifting it up for inspection, Abby has opened a whole new vista on the past and added, for this visitor at least, another layer to the rich history of one of the most picturesque spots on earth. Who would have thought that a 17th century tourist standing at this spot would have seen a quite different sight? This area, believe it or not, used to be a horrible eyesore, a blot on the landscape.

Those golden ruins of the refectory, glowing in the April sun where you can almost visualise ghostly monks eating their sombre meals, were put to a quite different use three centuries ago. The refectory was a warehouse crammed with charcoal for use in the blast furnaces that were going full-pelt in the valley.

Forge Cottage, which we have just passed on our walk, has that name for a reason. Those humps and lumps around it, which just seem part of the wonderful natural landscape, are old slag mounds.

Iron ore, mostly mined at nearby Bilsdale, was carted here for the smelters to do their work. The rich varieties of timber that had graced the steep sides of the pretty valley were wrecked to feed the demands of the iron industry. The solitude which had first brought the Cistercians here was gone and so was their goal of a life lived in harmony with nature. Meditation and calm had been replaced with smoke and noise.

The Romantic imagination, through poets and painters, has conditioned us today to see bare ruined choirs and similar ruins of the great religious orders as poignant. It's taken as read that what brought them to this state was deeply regrettable – acts of monstrous vandalism by Henry VIII who wanted their wealth for himself. But thinking about the significance of the lump of slag suggests a different view of things. Maybe for the people who were trying to make a living round here after Rievaulx had fallen under the axe of the Dissolution in 1538, there was no reason for sentiment or sadness.

Maybe the locals here were glad to see the back of the monks, if their departure signalled a rapid expansion of industry. For ordinary people, being a bit dirtier might have seemed a price worth paying if it meant becoming quite a bit wealthier.

This is just a tourist's instant revisionist view of history and possibly quite fanciful. But at least it gets the imagination working and that seems to be the sort of response that Abby Hunt is hoping for. She is an archaeological investigator for the research department of English Heritage and has hosted our hour-and-a-half walk from Helmsley Castle to Rievaulx.

It's part of an English Heritage programme which aims to open the eyes of the public to what they are seeing at historic sites. On this afternoon, Abby is working in tandem with Simon Bassindale, a North York Moors park ranger, and in their company the secrets of the history of the area and its wildlife open like the pages of a book as we
step out.

This well-informed progress along one of the most historic trackways in the land is being repeated for the public over the May Bank Holiday weekend. It starts at Helmsley since this was where the story began. It was home to Walter Espec, the man who set up Rievaulx Abbey and Kirkham Priory as well. Maybe he feared there were a few sins which needed expiating while he had the chance. The genocidal tendencies of his predecessors were well-remembered, recorded in the Domesday Book by those areas where nothing was left to tax following the early depredations of the Norman conquerors.

Most of the castle's stonework date from the 12th and 13th centuries and in Elizabethan times the Manners family remodelled part of it into a mansion. What you see today are the ruins that Cromwell knocked about a bit. His men under Sir Thomas Fairfax besieged the castle for three months in 1644 before the Royalists surrendered.

The walk takes us past the castle earthworks and up a slope where Simon Bassindale points out the curlews who have come back in the past three weeks, having over-wintered on the coast. One of his colleagues has seen the first two swallows. They had a good early daffodil season, but now the flowers have gone into shut-down mode during the cold snap. At least that should prolong the season. As we climb, Griff Farm appears to the right. This is within a field's distance of where Rievaulx Abbey's Grange was sited and takes local agriculture back 1,000 years. Granges were farmsteads run by the lay brothers of a monastic house who were not required to do the daily offices of the monks. Each grange was supposed to be within a day's travel of the main house so they could in theory return for worship.

This is about as high as you can get, on this broad plain, for good cultivation. It's limestone country and the path leads to a steeply incised valley, typical of the locality, caused by glacial melt being forced into narrow channels and quite unlike the valleys in the sandstone slightly further north. We plunge down to the bottom Black Howl (howl meaning a wood). According to Simon, the locals are not keen on coming here. As an East Riding man, he can't see what there is to worry about. There's history to be seen here too, but it only goes back 60-odd years. It's in the shape of rusty bits and pieces left behind by Second World War tank units, mostly Polish and Canadian regiments, who were stationed in the vicinity. A few strides further on and we are back to the 18th century as we cross the long carriage drive from the Baroque mansion of Duncombe Park, completed in 1713, to the terraces and the temples laid out on the escarpment overlooking Rievaulx. Looking to the forested near horizon, we switch in time back to the monks again. On these slopes are veteran trees 1,000 years old.

We pass the remains of a quarry, one of eight or nine dotted around. A constant source of stone was needed at the abbey for expansion and repairs. Experts have analysed the chemical make-up of the stones and tied that information into the various building phases of the abbey

The road below cuts through another sharply-contoured valley above which sits Abbot Hagg farm (a hagg being a coppice). Visible by the side of the road are the reasons for the farm's name – the ash trees coppiced to provide the handles for any number of implements and tools for generations of monks and farm workers. In its heyday, Rievaulx had 140 monks but it had its ups and downs. In the 1380s, after the Black Death had done its worst, there were 15 monks and three lay brothers. There were only 21 when Henry VIII's henchmen showed them the door.

The nature of the lives they led comes into sharper focus when put into a broader context by experts like Abby and Simon. "We want to alert people to the wider setting, that all these things you see on this walk co-existed and were mutually dependent," says Abby. "They are all tied together with the landscape."

In short, don't just think of this as a ruin, a teashop and a safe drive home. There's a lot more more around here than meets the uninstructed eye.

n English Heritage and the Can Do Partnership host a pilgrimage over the May Day bank holiday weekend (May 4 & 5) when visitors can join a walking tour between Helmsley Castle and Rievaulx Abbey, following a route through Duncombe Park and showing how important the area has been throughout the centuries, as well as looking at some of the wildlife.

Reserve your place on 01439 770442

www.english-heritage.org.uk/helmsley