The integration of the wave energy devices (WECs) into existing or new coastal structures could be a realistic solution to reducing their very high costs (Vicinanza et al., 2014). Nowadays very few devices have been constructed in full scale and no one is in commercial phase. The paper presents the prototype of an innovative breakwater for wave energy conversion installed in the port of Naples in 2015. The device is denominated OBREC (Overtopping BReakwater for Energy Conversion) and represents the world’s first WEC prototype completely embedded into a breakwater, which exploits the wave overtopping process. This article shares the entire design process, from concept, the preliminary design in small scale to the full-scale prototype construction.