The Upper Province is a half of the Centauri Princess' 6 x 9 mile cylindrical biosphere.
Map of the Upper Province
The Upper and Lower provinces are a 50-50 split of the total curvilinear habitable surface of the 6 x 9 mile cylindrical interior of the Ark. They were originally divided in this way to serve as a means for convenient geographic referencing of places, akin to how we divide the spherical surface area of planet Earth into a Nothern Hemisphere and a Southern Hemisphere.
The Upper Province contains the residential town of Utopia and the Navigation and Control Complex.