The flow physics associated with the interaction of a low aspect ratio, cantilevered cylindrical pin with a flow over a flat plate was investigated experimentally using oil visualizations and stereoscopic particle image velocimetry. The interactions of the vortical structures were explored for laminar, transitional and turbulent incoming boundary layers, where the flow's sensitivity to the pin's aspect ratio and its relative submergence within the boundary layer was studied. The surrounding flow is highly sensitive to subtle changes in these parameters (both are order 1) due to strong dependence between the flow over the pin's free end and its wake. These flow structures are heavily influenced by competing mechanisms of self-induction and shear flow due to outer fluid entrainment and the proximity to the wall. In particular, the observed vortical features exhibit strong inter-dependencies in the near wake. For a turbulent boundary layer, the resultant ‘arch-like’ structure is observed to be slightly stretched in the axial direction. Whereas, under laminar inflow conditions, the reduced shear and turbulence intensity facilitate a wider wake and a stronger downwash from the leeward edge, resulting in a concave ‘M-shaped’ vortex, affecting the formation and evolution of the trailing vortex pair. In addition, larger aspect ratios result in an increased magnitude of downwash into the wake, which re-energizes the near-wall flow. Whereas, for lower aspect ratios, the level of interaction between vortical features decreases due to a reduced downwash and weaker shear. These flow characteristics are discussed in detail in the paper.