We propose a VLBI absorption line study to locate and image the absorption of excited OH at 6 GHz from a putative molecular torus. For this we selected two nearby type-2 AGN: NGC4261 and NGC3079. With this we can test or possibly refine the Unfied Scheme model, in which a circum-nuclear torus determines the appearance of an AGN, depending on viewing angle and torus geometry (thickness, inner and outer radius). This study will provide a) direct view of the obscuring material, determine b) its location relative to VLBI core, jet and counter-jet, c) its velocity, and d) opacity. Facilitated by the ~1 mas VLBI beam, all of the above is obtained with a spatial resolution, which matches the expected dimension of the circum-nuclear matter (sub-pc scales). A combined study of 22 GHz H2O maser and 6 GHz OH absorption will also allow us to i) clarify the nature of water maser in the elliptical galaxy NGC4261 and to reveal kinematic connections among radio jet, disk or jet maser, and obscuring matter.
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