Density-functional calculations are carried out to explore more intensely on geometric, spectroscopic and electronic properties of the neutral Au16. Computed results show that the cluster does not form a hollow cage structure as in its anionic state but prefers a compact structure, giving rise from the cuboctahedron Au12 capped with four gold atoms on triangular faces. The ionization energies for lower-lying isomers are also computed and compared with available experimental values. Although several isomers are predicted to be very similar in energy, the corresponding vibrational signatures are so distinctive that could be used as a fingerprint signal to identify their geometrical structures. In addition, the electronic and atomic structures of this system can be understood in terms of the phenomenological shell model.