Apparently, Ukrainian drones pushed through and started a chain reaction.
Explosions reportedly continued for hours, and authorities evacuated nearby settlements. Initial reports indicate that the site, previously protected by one of Russia’s densest air defense networks, suffered catastrophic damage.
Assuming I’m looking at the right thing on google maps, it does seem to be a lot of earthen bunkers with berms separating them. There are also quite a few free standing buildings scattered around.
I looked at Hawthorne Army Depot (US) to compare, and that one is a lot less dense, but it’s absolutely gigantic.