Official version of Vatikan
Vatikanstadt is currently written as Vatikanstaat. Wikipedia says the official version in Germany is Vatikanstadt, even though "Vatikan, Vatikanstadt oder Vatikanstaat" is also allowed. Since the wikipedia page title is with Stadt, i would go for Vatikanstadt instead of Vatikanstaat
#1 Updated by Simon Schaufelberger about 3 years ago
even on their official website it is written as Vatikanstadt.