  Computer simulations of a model glass-forming system are presented, which are
particularly sensitive to the correlation between the dynamics and the
topography of the potential energy landscape. This analysis clearly reveals
that in the supercooled regime the dynamics is strongly influenced by the
presence of deep valleys in the energy landscape, corresponding to long-lived
metastable amorphous states. We explicitly relate non-exponential relaxation
effects and dynamic heterogeneities to these metastable states and thus to the
specific topography of the energy landscape.
