Not the first map I've ever made but the first I've submitted - intended entirely to test the capacity to defend against increasing waves of invasion.
Karst geography in the surrounding uplands makes the main gate a bottleneck point, as does the peninsular location of the keep on what appears to be a volcanic plug.
Both a short siege and the full invasion (with complete and incomplete castles respectively) are in this package.
The invasion is considered the primary mission.
Update: Whilst you *could* get a lot of stone by tearing down the sea barricades, this may make your mission a little harder, later, as leaving it in makes for *really* good target practice for catapults. And who would ruin a perfectly beautiful facade like that anyway?