The tour group looked at the hatchet marks, still visible today on the concrete floor. “These were the inmates that fared the worse,” corrections officer and tour guide Trinidad Torres told us, pointing to the marred grooves, while 15 engrossed tour members listened intently. We were in cell block 4 of the “Old Main” Penitentiary of New Mexico (PNM), where in 1980 one of the most violent prison riots in American history erupted.