Looks like a red + in the overmap, and is FULL of food and other goodies.
Got one generated and was a very good surprise but after I save&quitted the save directory was empty 
Last Man On Earth(LMOE) shelter one of the best locations there is, usually in remote locations so no suprise Zs arrive to keep you company while you sleep, their stuffed with food and a couple of guns and the best thing, matching ammo for them, infinite water supply, a stove so you don’t burn it down cooking and a bunch of crates that are usually empty but make good storage.
They’re handy, cos of the stream running through the basement where the stove is.
However, if you can find a town near a river, and clear out a section for yourself, that kinda becomes irrelevant.
I’m planning on making the LMOE shelter a bit more dangerous. But that depends on a different project I’m working on.