Middleton Mine is the only underground Limestone mine in the UK. The mine itself is split over three levels and stretches for 25 miles underground. Its unclear when the mine originally opened but its origins date back to when one part of it was used for lead mining. It was only in the 1900s that the mine turned to Limestone mining.
The mine has been disused since 2005, however it forms part of a strategic reserve and could be brought back into use.