Sneak of the Dead
The safest place you can possibly be in the event that hell runs out of space and the dead walk the earth is in a movie theater. Let's discuss.
There's usually a point in a zombie movie where the snacks...er...protagonists manage to barely escape the horde by running into a building and barricading the doors. There's just enough of a lull for you to think they might be safe for a while, then a zombie hand crashes through the window! And everyone is surprised!
Look, zombies may be mindless killing machines, but somewhere deep in the recesses of their virus- and voodoo-riddled brains, they remember that it is easier to get through closed windows that it is to get through closed doors. The movie theater, much like the shopping mall, is a superiorly defensible location because of its lack of windows. Why do you need windows after the zombie apocalypse? There's only two things you'll see if you look outside the theater: zombies or no zombies (indicating that they are hiding). Look, padlock all those helpfully highlighted exit doors and jack-knife a semi trailer in front of the ticket booths. You'll have plenty of room in the theater for storing supplies and even working plumbing for lots of people. Doors and windows are a liability.
2. Defensible Perimeter
So you have your theater sealed up as tight as a drum but still want to keep an eye on the undead menace? Head up to the roof. Unlike residences, movie theaters tend to have large, flat roofs with easy access from the theater itself. Not only can you safely get some air up there, it's a great place to collect potable rainwater in old popcorn tubs (provided the rain wasn't what zombified civilization in the first place). It also serves as a safe lookout post and place to signal other survivors. If you think there might still be some military air cover, you can arrange ripped-out theater seats into a message. Really, though, the roof comes to greatest advantage when combined with what's next on our list.