The Citadel prison in Hajin is a good spot for looting valuable resources, guns, keys, and rare weapon manuals. The location has a mix of critical and extreme threat levels, but it offers some valuable loot. To access this area, choose the story mission called Operation Iron Citadel, which spawns you close to the POI at the start of your match. Follow the outer wall of the Chang-san Air Base, vault over a broken wall, and loot all three barrack-style buildings, searching soldiers' lockers and duffle bags for decent armor vests, high-value printer resources, keys, and weapon manuals.
Other good loot locations in Hajin include the NurigoGO Mall, Cheonwang Peak Array, and Haneul Nuclear Reactor. NurigoGO Mall offers a wide range of items, including guns, medical supplies, and printer recipes, but be cautious when exploring the subterranean sections. Cheonwang Peak Array has a medium threat level and offers great loot opportunities, including safes with gold bars, keys, and valuable printer resources. Haneul Nuclear Reactor is a high-risk location with high-reward potential, offering the chance of weapon manuals, high-value keys, and high-rarity resources like Power Regulators.