the Abe Friedman Occupational Center is one of them. it used to be beautiful old building, now its a butt ugly windowless 10 story concrete structure built like a aboveground air raid shelter.
1646 South Olive Street, Los Angeles, California
it has 10 floors up, a basement, a subbasement, and a sub-sub basement (3 floors below ground)
I sneaked into the sub-sub basement, its not lit and really creepy. appears to have a bomb shelter. although the building above would of sufficed just fine.
IKEA- like having a 112 room 350,000 sq foot house. it has everything and sometimes multiple copies of everything. there are few ground floor entry points, its made of premanufactured concrete slab constructions, huge flat roof suitable for some gardening, and a massive parking lot around it that gives you a nice 200+ yard clearing to make into some kind of no-man's-land. skylights for venting and allowing light into the otherwise windowless structure. actually mine has windows, but not enough of them.
what it lacks is food, water & power. it has everything else.
Super Walmart, like the one in Santa Clarita, California. if you like walmart, then one is like going to walmart heaven. its huge, inside its neat, brightly lit, and very welcoming. and sam's club is right next to it. there's many skylights to bring natural light in, few entryways, has everything and then some, even though in CA it doesn't sell guns it has lots and lots of ammo. again concrete structure, standalone construction ( besides the sams' club), surrounded by a huge parking lot.
it being 100+ miles from my house, I've only been there 3 times, but each time it was a great experience. its not like the other walmarts which i often find to be dingy, depressing, poorly lit, disorganized, full of lazy, incompetent employees that wish not to be there, and parking lot is always full of idiot drivers that make you scared to park there because you don't want your car dinged up or backed into. and don't mean to be racist, some of the my local walmarts its like going to a Mexican one, everything is in Spanish. I hate that, this is the USA, where we speak, read & write english, I had to learn it, so should everyone else. the Spanish irritates me, its like as if California is part of Mexico.
a real gun store, like ammo bros, ade's gun shop, or B&B guns. if you didn't get filled with lead upon entry. they have a security cage that if you enter, requires someone up near hte cashier to press a key so you can enter the store. the windows are barred, the place is like a fortress. ammo bros has an in-house reloading shop. ade's, a gunsmith, and B&B guns just has everything gun-related.
I think the idea they had in Resident Evil Afterlife with the prison as a holdout was a good one. The Milton Penitentiary is about 30 minutes from my place and they have riot gear, 30ft high walls, generators (provided fuel can be salvaged). Unfortunately because it's a Canadian prison it has no firearms, but there is a police division 1km away from it for the purpose of providing support from ERT. That means the weapons wouldn't be civilian grade. Plus the watch towers would be good, and though all the doors and such are run off of a system the old key and lock still works for if there was a power disruption.
To me it seems like a damn good place to hold up. With a really good team you could probably turn it into one hell of an operations centre.