We examine the diffusive behavior of single polymers under spatially varying entropic confinement. A nanofluidic slit embedded with a lattice of pits was used to constrain single DNA molecules to discrete conformational states. Diffusion was characterized by dwelling in specific conformations followed by transitions to neighboring states. In contrast to studies involving simple 2D (nanoslit) and ID (nanochannel) geometries, the diffusivity showed nonmonotonic dependence with respect to the parameters of confinement. In particular, the nanopit array allows us to fine-tune the diffusivity of a single polymer to a local resonance minimum. Moreover, we show that energetically favorable states dominate over higher energy states and that a single state can be stable over a wide range of parameter space. These stable states correspond to resonances in the diffusion.