[en] Tunneling phenomena occuring in potentials with several minima are discussed using a generalization of Landau's approach. In particular, the strong influence of the shape of the potential on the tunneling probabilities (resonances) and on the shape of a time-dependent wave packet (coherence) is shown for the case of the asymetric double square-well potential. Finally, these features are illustrated for more realistic potentials by numerically solving the time-dependent Schroedinger equation in one and two dimensions. (orig.)