  Tidal streams of globular clusters are ideal tracers of the Galactic
gravitational potential. Compared to the few known, complex and diffuse
dwarf-galaxy streams, they are kinematically cold, have thin morphologies and
are abundant in the halo of the Milky Way. Their coldness and thinness in
combination with potential epicyclic substructure in the vicinity of the stream
progenitor turns them into high-precision scales. With the example of Palomar
5, we demonstrate how modeling of a globular cluster stream allows us to
simultaneously measure the properties of the disrupting globular cluster, its
orbital motion, and the gravitational potential of the Milky Way.
