A complex active region was observed simultaneously with the solar telescopes VTT and THEMIS on Tenrife in May 2005. Spatial scans across the sunspot group were performed at both telescopes. The full Stokes-vector was recorded in several photospheric spectral lines, i.~e. at the VTT in a group of iron and silicon lines in the near infrared and at THEMIS in iron and chromium lines in the visible. Inversions were carried out independently for the different lines in order to derive the magnetic field strength, its inclination and azimuth together with the temperature stratification. Thus we obtained the three-dimensional structure of the magnetic field. Selected locations in the penumbra and in light bridges were considered in detail. We find a general tendency that the magnetic field is weaker and less inclined in higher layers.