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We present a method to obtain reddening maps and to trace structure andmetallicity gradients of the bulge using data from the recently started ESOpublic survey Vista Variables in the Via Lactea (VVV). We derive the mean J-Kscolor of the red clump (RC) giants in 1835 subfields in the Bulge region with-8<b<-0.4 and 0.2<l<1.7, and compare it to the color of RC stars in Baade'sWindow for which we adopt E(B-V)=0.55. This allows us to derive the reddeningmap on a small enough scale to minimize the problems arising from differentialextinction. The dereddened magnitudes are then used to build the bulgeluminosity function in regions of 0.4 x 0.4 deg to obtain the mean RCmagnitudes. These are used as distance indicator in order to trace the bulgestructure. Finally, for each subfield we derive photometric metallicitiesthrough interpolation of red giant branch colors on a set of empirical ridgelines. The photometric metallicity distributions are compared to metallicitydistributions obtained from high resolution spectroscopy in the same regions.The reddening determination is sensitive to small scale variations which areclearly visible in our maps. The luminosity function clearly shows the doubleRC recently discovered in 2MASS and OGLE III datasets, hence allowing to tracethe X-shape morphology of the bulge. Finally, the mean of the derivedphotometric metallicity distributions are in remarkable agreement with thoseobtained from spectroscopy. The VVV survey presents a unique tool to map thebulge properties by means of the consistent method presented here. Theremarkable agreement between our results and those presented in literature forthe minor axis allows us to safely extend our method to the whole regioncovered by the survey.

Reddening and metallicity maps of the Milky Way Bulge from VVV and 2MASS. I.The method and minor axis maps