Ion hydration and transport at interfaces are relevant to a wide range of applied fields and natural processes. Interfacial effects are particularly profound in confined geometries such as nanometre-sized channels, where the mechanisms of ion transport in bulk solutions may not apply. To correlate atomic structure with the transport properties of hydrated ions, both the interfacial inhomogeneity and the complex competing interactions among ions, water and surfaces require detailed molecular-level characterization. Using a noncontact atomic force microscopy (AFM) system, we were able to image the individual ion hydrates at surfaces with atomic resolution. We found that the alkali ion with specific hydration numbers diffuses orders of magnitude more quickly than other ion hydrates, arising from the degree of symmetry match between the hydrates and the surface lattice. In addition, we found that the alkali ions can come into close contact with each other through the dehydration and water rearrangement process, which is driven by the effective ionic attraction due to the interplay between the water-ion and water-water interactions. These results not only help us to understand the nature of biological ion channels, but may also provide general design principles for artificial ion channels towards high permeation rate and selectivity.