Decades' worth of litter has produced a strange formation in the darkness

*The tunnel is not maintained, and is not safe. Do not try to gain entry.

Nottinghamshire's underground spaces have held people's attention for decades - just look at the sandstone caves of the city. But what about the places nobody's allowed to see?

Urban explorer Lost Places & Forgotten Faces recently visited an abandoned railway tunnel. Mapperley Tunnel was in use from 1875, but repeated problems such as a cave-in and subsidence forced it to close in 1960.

It's what has happened to it since then that makes it unique, though. Decades' worth of litter has been poured down an open hole into the tunnel, forming what some call the "Mapperley Stack".

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A spire of discarded items rises in the darkness, almost like it was deliberately made as a statement. Folding chairs, pipes and tyres, plastic sheets and more, all held together in an unrecognisable mash of waste.

Take a look at the photos below to see what's happened to this once-vital connection since its closure in 1960.

*The tunnel is not maintained, and is not safe. Do not try to gain entry.

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Graffiti on the walls, beside the "Mapperley Stack" of rubbish coming through the hole in the ceiling.

The "Stack" itself, coming through one of the air holes in the tunnel ceiling.

A broken brick wall, as the tunnel descends into darkness.

More graffiti, usually invisible in the dark.

Daylight at the mouth of the tunnel.

The mouth of the tunnel in the overgrowth.

Either side of the tunnel mouth are these people, in white, faded paint.

Tracks once led the tunnel, which you can just make out in the middle of the picture.