  There are theories of coverings of $C^*$-algebras which can be included into
a following list: coverings of commutative $C^*$-algebras, coverings of
$C^*$-algebras of groupoids and foliations, coverings of noncommutative tori,
the double covering of the quantum group $SO_q(3)$. This work is devoted to a
single general theory which includes all theories of this list, i.e. we develop
a system of axioms which can be applied for every element of the list.
Otherwise since topological coverings are related to the set of geometric
constructions one can obtain noncommutative generalizations of these
constructions. Here the generalizations of the universal covering space,
fundamental group, Hurewicz homomorphism, covering of the Riemannian manifold,
flat connection are explained. The theory gives pure algebraic proof well known
results of the topology and the differential geometry. Besides there are
applications of the theory to (unbounded) operator spaces and this theme is
also discussed here.
