  Two different constructions of an invariant of an odd dimensional hyperbolic
manifold in the K-group $K_{2n-1}(\bar \Bbb Q)\otimes \Bbb Q$ are given. The
volume of the manifold is equal to the value of the Borel regulator on that
element. The scissor congruence groups in non euclidian geometries are studied
and their relationship with algebraic K-theory of the field of complex numbers
is discussed.
