Dancing Hoskuld
Deity
Neither, there is an abatis improvement that provides 10% defensive bonus to a tile and acts as a city which is unlocked at Shelter building.
the palisade gives 15% defensive bonus, and is unlocked at carpentry.
It does not act like a city. That tag is false and I expect that is where the problem lies in the merge of Super Forts and our use of them in conjunction with ZoC. I suspect that some code checks that they have that tag set whereas other code does not, it just assumes that all fortifications do "act as a city".