  It is often assumed that a warped galaxy can be modeled by a set of rings.
This paper verifies numerically the validity of this assumption by the study of
periodic orbits populating a heavy self-gravitating warped disk. The phase
space structure of a warped model reveals that the circular periodic orbits of
a flat disk are transformed in quasi annular periodic orbits which conserve
their stability. This lets us also explore the problem of the persistence of a
large outer warp. In particular, the consistency of its orbits with the density
distribution is checked as a function of the pattern speed.
