Likely a quarry run by a local prison, the quarry is designed to supply forced labor to inmates. The labor serves to punish them with hard work in the hot sun as well as wear them down so they won't go to escape. The inmates are forced to use picks, shovels and sledgehammers to break down large chunks of rock, which are blown off the side of a nearby mountain by dynamite charges. Rambo is first shown using a chisel and sledgehammerinterested in carving the rock into smaller bricks. The quarry is guarded by police supervisors armed with shotguns and rifles.
The novelization gives more detail on the quarry.
- Rambo: First Blood Part II