We generalize the geometrical description of CP violation in the Standard
Model in terms of a unitarity triangle. For three left-handed Majorana
neutrinos CP violation in the lepton sector is determined by three unitarity
triangles. With three additional right-handed neutrinos 15 quadrangles are
required to characterize CP violation. We show the relation of the unitarity
polygons with physical observables.Comment: Revtex, 6 pages, 5 eps figures. Some typos fixed and a reference
added. To appear in PR
