  "Almost all" seems to be known about isolated stationary black holes in
asymptotically flat space-times and about the behaviour of {\em test} matter
and fields in their backgrounds. The black holes likely present in galactic
nuclei and in some X-ray binaries are commonly being represented by the Kerr
metric, but actually they are not isolated (they are detected only thanks to a
strong interaction with the surroundings), they are not stationary (black-hole
sources are rather strongly variable) and they also probably do not live in an
asymptotically flat universe. Such "perturbations" may query the classical
black-hole theorems (how robust are the latter against them?) and certainly
affect particles and fields around, which can have observational consequences.
In the present contribution we examine how the geodesic structure of the static
and axially symmetric black-hole space-time responds to the presence of an
additional matter in the form of a thin disc or ring. We use several different
methods to show that geodesic motion may become chaotic, to reveal the strength
and type of this irregularity and its dependence on parameters. The relevance
of such an analysis for galactic nuclei is briefly commented on.
