In a time where no satellites and computers provided you with quick and detailed maps, cartography was a commission even more ambitious that a sculpture or a painting. Just like tapestries, decoration and practical use were satisfied in one piece.
Pope Gregory XIII, so fascinated with science, sent geographers all over Italy to draw maps of the peninsula, modernly envisioning the country as one whole, rather than a puzzle of independent states.
After four hundred years, the maps are so accurate you could still use them to travel today. Sicily, Calabria, Tuscany, Veniceall the regions are painted as frescoes with rich decorations and meticulous details. If you have traveled in Italy, it is amusing to compare the places you have visited with their depiction of so many centuries ago.
Unmissable is the heavily stucco and gold decorated ceiling, one of the finest in the whole Vatican.