The aim of this investigation is to provide an experimental volumetric visualization of the near wake topology of the vortex structures generated by a flapping-wing Micro Air Vehicle (MAV) by means of large-scale Robotic PIV. This novel technique implements coaxial illumination and imaging in combination with the use of Helium Filled Soap Bubbles (HFSB) as tracing particles to achieve large measurement volumes of the order of 10 liters. Information of different phases throughout the flapping cycle is obtained by means of a phase-locked averaging procedure. Experiments in both tethered and free-flight conditions have been performed, yielding an unprecedented comparison between the aerodynamics of the two conditions.