This is the weirdest underground place I have ever been to, mainly as it hasn't always been underground.
Firth Brown was one of the steelwork giants in Sheffield, with the medical centre there to look after any injured workers from the factories.
There is no information on when it closed down, but the picture to the right suggests it was still open in 1956.
What makes this place so special is the fact that the building was never demolished once the doors were closed. Instead a wall was build around the whole complex. The top was then filled up with gravel and it now serves as a car park raised a storey above the road. The reasons for this I can not understand.
I have been in many underground locations and it's always a little worrying thinking about the tonnes of soil sitting just a metre above you. But in this case it was even worse, as only an 80 year old ceiling of a small building was holding up this weight it was never designed for.
The place isn't very big, but with its history and also the ingenious access it was definitely worth a look.