Galactic structure and stellar clusters in obscured Hll regions

Aiming to improve our understanding of the spatial distribution of Galactic HII regions we have started a program with the integral field spectrometer SINFONI on the ESO-VLT (Very Large Telescope) Yepun to observe obscured stellar clusters in HII regions. Through the detection and spectral classification of individual cluster stars we are able to obtain a complete census of the nature of the brightest stars and to obtain a spectrophotometric distance to the cluster. Such distance estimates are independent and complementary to kinematic distances and free from the ambiguity inherent to the latters' determination. Most importantly, our method is based on near-infrared observations, which are much less limited by interstellar extinction than previous optical programmes, allowing studies along lines of sight where optical measurements are impossible