Geometric Topology can be defined to be the investigation of global
properties of a further structure (e.g. differentiable, Riemannian,
complex, algebraic etc.) one can impose on a topological manifold. At
the C.I.M.E. session in Montecatini, in 1990, three courses of lectures
were given onrecent developments in this subject which is nowadays
emerging as one of themost fascinating and promising fields of
contemporary mathematics. The notesof these courses are collected in
this volume and can be described as: 1) the geometry and the rigidity of
discrete subgroups in Lie groups especially in the case of lattices in
semi-simple groups; 2) the study of the critical points of the distance
function and its appication to the understanding of the topology of
Riemannian manifolds; 3) the theory of moduli space of instantons as a
tool for studying the geometry of low-dimensional manifolds. CONTENTS:
J. Cheeger: Critical Points of Distance Functions and Applications to
Geometry.- M. Gromov, P. Pansu, Rigidity of Lattices: An Introduction.-
Chr. Okonek: Instanton Invariants and Algebraic Surfaces.