Are citadels going to be worth building?

[Sphinx]

Citadels would be awesome for a turtling player who doesnt let players get close to their cities and is only defending. (to win by culture or schience). PLace them so they cover the borders and have few strong units there, including ranged.

 

[Pragmatic]

I don't know what the effect of a unit taking the citadel is.

Citadel belongs to whomever owns the tile (i.e., within their cultural radius). If an enemy takes the citadel, it's the same as an unmodified tile for them. (Don't have a page # from the manual, sorry...)

Don't know if they can raze it, though.

 

[Olleus]

From the manual:

Once a civ has acquired the Engineering technology, workers can construct “forts” in friendly
or neutral territory. Forts provide a hefty defensive bonus to units occupying them. Forts
cannot be constructed in enemy territory. If a unit enters a fort in enemy territory, the fort is
destroyed. Forts can be constructed atop resources.

I would assume that citadels work the same way, but instead of becoming completely razed, they become semi-pillaged, and have to be repaired by a worker before it provides any benefit again.