Layout of the XMM XXL observations; only survey-type observations are indicated in the figure. Top: XXL-N. Bottom: XXL-S. The footprint of the XMM observations is shown on maps of dust column density calibrated to E(B−V) reddening in magnitude (Schlegel et al. 1998); the circles have a diameter of 20 arcmin (the entire XMM field of view encompasses 30 arcmin). The blue circles show the pre-XXL observations and the light blue circles indicate the pre-XXL observations done in mosaic mode. The red circles stand for the XXL AO-10 observations, all of which were done is mosaic mode. Already existing observations completed to 10 ks within the AO-10 time-allocation are marked by a red dot.