  In [1], KKLT give a mechanism to generate de Sitter vacua in string theory.
And the scenario, \emph{Landscape}, is suggested to explain the problem of the
cosmological constant. In this paper, adopting a simple potential describing
the \emph{landscape}, we investigate the decay of the vacuum and the evolution
of the universe after the decay. We find that the big crunch of the universe is
inevitable. But, according to the modified Friedmann equation in [11], the
singularity of the big crunch is avoided. Furthermore, we find that this gives
a cyclic cosmological model.
