  Order of magnitude estimates of radiogenic heat and antineutrino production
are given, using the San Marco cathedral as an example. Prospects of
determining the radiogenic contribution to terrestrial heat by detection of
antineutrinos from natural radioactivity (geoneutrinos) are discussed. A three
kton scintillator detector in three years can clearly discriminate among
different models of terrestrial heat production. In addition, the study of
geoneutrinos offers a possibility of improving the determination of neutrino
mass and mixing, by exploiting the knowledge of Th/U abundance in the Earth.
