I'm making a list (Ten Mostly Zombie-Proof Buildings of the Ancient World) of ten ancient buildings that could easily fend off Max Brooks' Survival Guide type zombies, and seem to have been made for that purpose.
However, as you may see by the link to the work in progress I gave you, I only have three so far. I really only know about my little corner of the world, and that's not all that much of the ancient world.
If you have an idea to give me, I'll credit you (using a name you give or your user name) at the beginning of the item you suggested. Please give reasons why your chosen man made structure is zombie proof (mostly), and try not to list anything that was made too recently. Also, the building must still be around (no Library of Alexandria).
Also, critique or suggestions on the list so far is appreciated. Thanks in advance for assistance!
Most zombies cant climb at all, and if they can, not very well. Fast zombies might be able to however.
My suggestions are the Pyramids of Giza, the Great Wall of China, many portions are preserved and fortified, the Coloseum of Rome... hope that helps a bit.
I think you could hold out here for quite a while.