This review article presents a state-of-the-art review of the ring and wall interactions in the case of normal and oblique collisions. The different approaches used to study this flow and the results obtained are described and discussed. These techniques span from flow visualizations to LDV measurements, direct numerical simulations, particle-in-cell vortex methods and viscous and inviscid interactions. The relevance of these basic flows to the comprehension of wall-turbulence is also described. Finally, further developments, such as interaction with a grooved surface and with a deformable wall, and in Non-Newtonian fluids, are suggested.