megaprison

noun

1. (informal)An extremely large prison.

   “Some 64,000 people have been arrested since the state of emergency began, some of whom have been transferred to a megaprison earlier this year.”

   “More than 3,000 people have been arrested since Jan. 9. The police have even released images of some detainees stripped down to their underwear, recalling images from Mr. Bukele's infamous megaprisons.”