Sources of UHE cosmic neutrinos must be seen in the sky in the accompaning radiations, most notably high energy gamma radiation. The main interest of neutrino astronomy is in the sources not seen in other radiations, so called "hidden sources". I will review the models for such sources and discuss, in particular, two recently suggested hidden sources: topological defects in the mirror universe (Berezinsky and Vilenkin 1999) and a stellar cluster at stage of black hole formation (Berezinsky and Dokuchaev 2000).