Location of the subsystems of GPAO within the structure of the unit telescope. The beam of light is represented in light red, from the vertical incidence on M1 down to the exit toward the VLTI tunnel. Although they are not formally GPAO subsystems, the location of the M2 mirror, the elevation and azimuth axes, the Nasmyth beacon, the mirrors of the Coudé train, the M9 dichroic, and the star separator are also highlighted because of their particular importance for GPAO.