  This work deals with relations between a bounded cohomological invariant and
the geometry of Hermitian symmetric spaces of noncompact type. The invariant,
obtained from the K\"ahler class, is used to define and characterize a special
class of totally geodesic embeddings, called "tight embeddings". In addition,
special isometric actions of finitely generated groups on Hermitian symmetric
spaces are studied. Results of a joint work with M. Burger and A. Iozzi about
surface group representations are also discussed.
