The deployment of this high-resolution seismic observatory consists of 2 lines of closely spaced (3-5 km) broad-band stations across the Cantabrian Mountains (Northern Spain) and several auxiliary stations at both sides of the profiles. By using techniques such as receiver function analysis and ambient noise tomography, this deploymet will allow us to improve our knowledge of the crustal structure and composition (e.g. Vp/Vs) of two key areas of this mountain belt that are subjected to intense scientific debates. It will also help to identify local active seismic sources.