The description for National visitor center says:
Must have built a Hotel in all Cities. The cost goes up the more cities there are in the empire. 100% of the Culture from World Wonders, Natural Wonders, and Improvements (Landmarks, Moai, Chateau) is added to the Tourism output of the city. Tourism output from Great Works +100%.
Does this mean that this wonder gives this bonus for all cities or just the one it is built in?