Think of St Paul's Cathedral and the amount of Portland stone that went into its construction, then try to imagine a corresponding hole in the ground and you might begin to visualise somewhere like Tout Quarry.
The quarry, just off the coast of Dorset, appears on tourist maps as a sculpture park. It is also a Site of Special Scientific Interest - but neither description comes within light years of doing justice to this place. I think it's the most inspiring, and surprising, 40 acres of ex-industrial land you can find anywhere in Britain.
As you approach by road from Weymouth, the "isle" (which is really a peninsula) rears up above you, dwarfing the terraces of Fortuneswell on its slopes. A series of hairpin bends takes you up above the town and out on to a plateau hundreds of feet above the English Channel.
Tout is the highest point of the peninsula - the name, pronounced "towt", is dialect for "lookout point". But entering the quarry through a tiny V-shaped gap in a stonewall, you are once again plunged into a very different world - a labyrinth of deep gullies rich in vegetation overshadowed by vast stacks of discarded rock.
When you've satisfied your childlike urge to scramble over boulders, you can start spotting artworks. There are said to be more than 50 here. Some, such as Antony Gormley's "Still Falling", a lifesize figure frozen in mid-dive, are carved directly into the rock walls. Others, such as Christine Fox's "Serpent Steps", follow and accentuate the landscape.
You are probably wondering how this rare collision of art, nature, industry and education came about. It was not by chance. Tout had been left to nature for almost a century when, in 1983, Britain's first open-air sculpture symposium was held here. The event was a huge success, and everyone involved knew it had to be continued. The Portland Sculpture amp; Quarry Trust was formed to develop an educational programme which would go beyond sculpture to involve geologists, botanists, landscape architects, film-makers and photographers.
Since then, Tout Quarry's owner, Hanson, Bath and Portland, has awarded a new 30-year lease allowing the project to continue. And the trust has gained the use of an old drill hall - with space for studios, exhibitions and a long-proposed education centre - through a partnership with Albion Stone Quarries and Crown Estate.
This could also see the project extending into two further disused quarries. Plans for Jordan Quarry include the use of its remaining limestone for works of art: one cubic metre a year, which would give it a new lease of artistic life for a good 100 years.
Portland Sculpture Trust, The Drill Hall, Portland, Dorset DT5 1BW A longer version of this feature appears in this week's TES
A longer version of this feature appears in this week's TES