A sophisticated adiabatic ground electronic state potential energy surface for a pure nitrogen ring (cyclic-N-3) molecule is constructed based on extensive high-level ab initio calculations and accurate three-dimensional spline representation. Most of the important features of the potential energy surface are presented using various reduced dimensionality slices in internal hyperspherical coordinates as well as full dimensional isoenergy surfaces. Very significant geometric phase effects are predicted in the spectra of rotational-vibrational states of cyclic-N-3. (C) 2004 American Institute of Physics.