Industry is nice when it’s old. In fact when industry has departed almost entirely but left some interesting traces, it becomes a heritage attraction. And in the case of Derbyshire’s Derwent Valley, it’s an official UNESCO World Heritage Site.

So many thanks to paternalistic Georgian mill-owners Jedediah and William Strutt of Belper, who built the house I’ve just been staying in, part of a model village for his workers. It’s the Derbyshire cotton and silk magnates who made this place what it is – all because of water power.

The Strutts are not so well known as Richard “Spinning Jenny” Arkwright at Cromford, just up the valley. But they were more progressive when it came to the well-being of their workforce. The long terraces of gritstone houses on stone-paved streets and rough alleys running up the hill from the river are compact but comfortable, with usefully large gardens, some with built-in pigsties. They were enlarged sympathetically in the 1880s. The terrace rooflines are often not stepped – instead they follow the line of the hill, so the top rooms are interestingly angled.

William Strutt’s North Mill of 1803/4 doesn’t look much from outside. It is rather overwhelmed by its huge redbrick Edwardian successor (in my picture, it’s the smaller building in the foreground). But it is fascinating, an early exercise in “fireproof” iron-framed construction. Understandably, given that Jedediah’s earlier (uninsured) timber-framed mill was lost in a fire. The younger Strutt adopted and adapted the recently-developed system by engineer Charles Bage. Slender cruciform iron columns are linked by long iron beams and lateral tie rods, allowing shallow brick arches nine feet across, stacked five storeys high and with a cast-iron roof. This is an early stab at what became your basic skyscraper system. And all the machines were powered from a huge cylindrical waterwheel underneath, fed by a lagoon made by damming the Derwent.

Engineering ingenuity is much in evidence here: the later Stephenson railway cutting through Belper, slicing right through the model housing, is a splendid thing of immaculately-dressed stone blocks, with many bridges in the same manner: it all integrates so well you are scarcely aware of the railway. Up the valley the Cromford Canal, an earlier Georgian achievement, makes its way to a lovely wharf terminus by Arkwright’s mills.  But oddest of all is the Tramway Museum, housed unexpectedly in a quarry at Crich. Working restored trams from all over Britain, Europe, even America are here.  Being Londoners, we took a London tram. It’s a surreal experience, travelling in such an urban vehicle high in the hills through woods, looking across the Derwent Valley. This part of Derbyshire is still not well enough known.  I can recommend it.