FOR CLARIFICATION:
EVERYTHING WAS SPAWNED IN BY ADMIN TOOLS! This is not a public server, though! I hosted this with my own money, just to play around with admin tools and to build some cool bases/drive around the map with cool cars or test weapons. No one has played on this server but me and my friends. I posted this so someone can take inspiration and rebuild this (for example) for a "Admins vs players base raid" event, build a safe haven for survivors on a RP server etc.
Building this took me somewhere around 2 weeks. It was worth it!