This article investigates the impact response of slender rockfall protection embankments, based on real-scale experiments. More specifically, it deals with rectangular in cross-section steep-sided gabion structures, designed to meet foot-print constraints. These three layered structures, 3m in width and 4m in height, are made up of gabion cages filled with different materials, depending on their location in the structure. Real-scale experiments were conducted with impact energies up to 2000 kJ on two structures differing by the fill material used for their kernel: ballast or sand-tire mixture. These experiments demonstrate the capacity of these slender structures in resisting high energy impacts. The response of these structures is also addressed considering data obtained using different measuring techniques and a large number of sensors within the structure. The results are presented and discussed with the aim of highlighting some issues associated to the structure impact response such as the load lateral diffusion, the stones crushing, the contribution of the wire mesh and the fill material characteristics. In the end, a structure with a kernel layer filled with ballast appears more efficient in reducing the structure downhill face deformation.