We explain how to construct a cluster algebra of finite type. The number of seeds in such a cluster algebra is the Catalan number. There is a fan, which I usually refer to as the cluster fan, whose maximal cones are in bijection with the seeds. We suggest how one might hope to construct Panyushev's conjectural involution on the set of ad-nilpotent ideals (whose cardinality is also the Catalan number) using Poincare duality on the cohomology of the toric variety corresponding to the cluster fan.