Left panel: spatial distribution of stars in the blue RC with 12.8 <K_s< 13.5 and 1.5 < (Z − K_s) < 2.0. Right panel: spatial distribution of stars in the red RC with 12.8 <K_s< 13.5 and (Z − K_s) > 2.1. These stars trace the location of the bulge dark lane. The innermost dark region with −1 <b< + 1 is populated by much more reddened RC giants and thus is affected by completeness. The source density is indicated in the vertical bar on the right, in units of 10³ sources deg^-2.