Olimpo
Vélez Sársfield, Argentina
El Olimpo was a clandestine detention center in Buenos Aires and used during the Dirty War in Argentina. Although it operated for only five months, from August 1978 to January 1979, about 700 people were illegally detained there, of whom only 50 survived. Jorge Fontevecchia, founder of the newspaper Editorial Perfil, was detained there.
Prison data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).