It was once a Royal Navy munitions factory.
Now sheep, the Army and occasionally movie makers have free reign within it.
Caerwent training area, in Monmouthshire, looks very much as it did in the 70s, when the manufacture of nitroglycerine and cordite finally ceased there.
This week, it's been the turn of the Royal Military Police to make good use of the derelict buildings as they run through several training scenarios.
The primary focus has been learning to deal with captured personnel, or "CPERS" (pronounced C-pers).
Captain Nathan Marsom of the Special Investigations Branch, 1 RMP (Royal Military Police) described the process by which CPERS are processed:
"CPERS will come in through the front door, and they'll be given a thorough all-over search - and that's looking for any items of contraband, anything dangerous, and anything that can be used to harm either themselves, or harm towards others as well".
He added that when this is done, CPERS are moved onto the medical bay. "We'll have a medical officer on site who checks over every single detainee that we receive into the facility. Once they've done that, they'll go on to our Day 1 Cell, and they'll go over all the documentation... once that's done, they'll be taken down to the holding cells".
Captain Marsom detailed how the documentation stage will determine exactly what kind of medical supervision a given prisoner shall receive, and how the holding cells can be used to bunch CPERS into appropriate groups, based on age, gender, or even family units.
The overall mission of this stage of the training is to ensure that detainees are handled humanely.
Lieutenant Colonel Gary McDade said:
"[As part of the training exercise], the International Community of the Red Cross will come and participate in the exercise, and they'll come and check that everything we're doing is humane, legal, and legitimate".
It's all been part of Exercise Redcap Charge, which sees a return to conventional war fighting, after the mission-specific training of Iraq and Afghanistan.
Elsewhere on the training area, another unit learnt to swiftly erect a traffic post so they might assist battle groups needing to cross any country in the world.
Moving the battle group through built up areas to reach war zones is also far from simple, so the military police laid out a map of the area they are exercising in, and used it to practice working out the most efficient routes for troops.
The military police have been given a vast range of scenarios to practice with, including genocides, downed aircraft, and fatal traffic accidents - with both regulars and reservists playing civilians, detainees and the enemy.
The end of Redcap Charge launches 1 RMP into their year at readiness, equipped and prepared to be sent anywhere in the world, should they be required.