An exhibition of Constable's little-known paintings of Cumbria opens next week. Helen Pickles set out to find those views again

The steep slog appeared pointless and my mind was turning to afternoon tea. Then I glanced left and the great domed head of Great Gable bore down on me. I scrambled higher. Yes, this was the spot! Great Gable, then a dip, then the long ridge up to Kirk Fell with its pimply cairn, and then on to the mass of Pillar. Perfect.

The scene exactly matched the image in my hand. Two hundred years ago, one October morning, John Constable had looked on this very view and whipped out his paintbrushes. I swear I was sitting on the same boulder.

Our greatest landscape painter is usually associated with sunny skies, agricultural domesticity and the flatlands of East Anglia. Yet in 1806, aged 30, he spent two months touring the Lake District: nothing gentle, nothing flat, nothing cosy. He produced 80 sketches and watercolours, experimenting with his technique. And for the first time those works are showing together in an exhibition at the Wordsworth Museum in Grasmere.

Constable visited after the Lake District was discovered - Thomas West's Guide to the Lakes was published in 1778 - but before mass tourism took off: the railways arrived in 1847. I wanted to see how the scenes looked today. He spent most of his time in Borrowdale - my starting point - amid overhanging crags, a meandering river, hidden side valleys, cottages and oak woods.

The first challenge was Lodore Falls: easy to find (north of Grange), but how things have changed. I could hear the cascade but no longer see it. Trees and the Lodore Falls Hotel obscured the view. The small bridgeis now swallowed up in the hotel's grounds.

The next challenge was Goat Crag (Gate Crag in Constable's day), just beyond the twin humpback bridges of Grange. Tricky: in Constable's day, there was no road. Squashing flat I did find the spot, though I suspect Constable stood nearer the banks of the river Derwent, now dense with trees. He painted the crag again a quarter of a mile further on, this time with the tooth-like Castle Crag in the foreground.

Rounding the next bend he must have got a surprise when the narrow valley opened out. Except for more tree cover the view was identical, the only difference the vapour trail of an aircraft across the sky.

Up the valley at Rothswaite, a tiny, whitewashed village, I fancy Constable was about to hike over the fell to Watendlath Tarn when he glanced back down the valley. And so he painted the "jaws of Borrowdale", a view more typically shown from the north. Through the "jaws", with Castle Crag guarding the left, I could glimpse, as he did, the end tip of Cat Bells, whose lower slopes descend to Derwentwater.

Next day, Constable tried my patience: I searched fruitlessly for his view of Helvellyn. (Weirdly, for all its 3,118 feet, Helvellyn is difficult to see close to as other fells get in the way.) I walked from the tiny church of St John's-in-the-Vale on to Low Rigg for Constable's northern panorama of Skiddaw, Lonscale Fell and Saddleback. Helvellyn, however, still niggled. On a hunch, I took the track south along High Rigg. Skylines began to slip into place. I scrambled up through bracken to a scree slope, turned round - and there she was; slap in the middle with the ridges of Striding Edge and Swirral Edge sharp as knife blades.

Journeying south, I stopped on Dunmail Raise, the high point separating Grasmere and the southern lakes from the north. The view through wide, scrubby valley slopes was uncannily similar, though the slick of water of Constable's day has grown and the shoreline is forested. In the 1880s, the valley's two small lakes were flooded to create Thirlmere, a reservoir to feed the cotton town of Manchester. Farms, communities, pubs - including the Cherry Tree Inn, visited by William Wordsworth - were lost. It provoked outrage, yet the conifer trees planted to stabilise the shores have softened Constable's stark scene, and you'd be hard-pushed to tell it's a reservoir.

My last stop was Langdale, where I walked up the narrow lane to Skelwith Fold, a wisp of a hamlet. In front of me lay the same mountainous skyline that Constable sketched at the start of his visit: Pike O'Blisco and Crinkle Crags with Langdale Pikes to Pavey Ark and Sergeant Man. Only tiny Elter Wateris now hidden by trees.

The pity is that only a few of these lyrical sketches and watercolours were turned into oil paintings. The bigger shame is that, today, no one knows where they are.

'Constable and the Lake District' runs from 1 July-31 October at Wordsworth Museum, Dove Cottage, Grasmere, Cumbria (015394 35544; Another exhibition, 'Constable: The Great Landscapes', is showing at the Tate Britain (020-7887 8888; until 28 August. Rydal Hall's gardens are open daily 10am-4.30pm (015394 32050; Helen Pickles stayed at The Borrowdale Gates Hotel, Grange, Cumbria (017687 77204; which offers half-board from £160 per night for two sharing a double room, and Storrs Hall, Windermere, Cumbria (015394 47111; which costs £245 per night on the same basis