A massive, salty filing cabinet

What should you do with the vast caverns left by Cheshire's salt mining? Fill them full of valuable documents of course.
During our lives, we all generate a vast paper trail of documents about us that need to be kept and archived. We rely on employers, doctors, councils, banks, the police and others to keep these details safe.
But - with so much paperwork - many filing cabinets and warehouses are full to bursting. So now many of our personal records are being transferred underground - to be stored down Britain's oldest working mine.
...
All this mining has left behind an awesome sight - a hollowed-out city the size of 700 football pitches, the roof propped up by vast pillars of rock salt that glisten almost pink under torch light.

Sounds like the Mines of Moria from Lord of the Rings.

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