The Lost Stronghold is a location that can be visited during the Always be Looting Event.
The Stronghold will have a banner atop the doorway such as ¨Fred´s Fort¨ or "Safe Here." These locations are surrounded by other exploitable buildings within a city. Inside they have high levels of zombies and lots of general loot. You will get a good amount of Gas, Food, Ammo, Medical supplies and even some higher tier weapons like Sledgehammers and Blowtorches. These buildings are laid out like a very large house.