Hunting for H_2O megamasers with the SRT

We outline a project that aims at using the SRT to detect 22 GHz water masers within the nuclei of galaxies. In some nuclei, the water masers populate accretion disks around the super-massive black holes, lying as close as 0.1 pc to the nuclear "monster". Once discovered, VLBI can be used to obtain a direct imaging of disk structures (typically obscured or not resolved by optical and infrared observations) and to derive important physical quantities (e.g. accretion rate, degree of disk warping and orientation, and the cosmic distance). Future extensions of this project to maser sources at cosmological distances, possibly leading to a direct measurement of the Hubble constant, are also briefly introduced. Technical and observing-time requirements for the outlined project are discussed.