  UNO (Underground Neutrino Observatory) is intended as a multi-purpose
detector, potentially useful for purposes which may not have been considered at
the time of its construction. UNO accomodates a comprehensive physics program,
encompassing nucleon decay and lepton flavor physics, including the possibility
of observing CP violation, grand unification scale physics, and detailed
observations of supernova explosions. The conceptual design of UNO is
described, along with specifics of how UNO would fit into an existing
commercial mine site in the western USA, which has been used as a strawman site
for planning and proposal development.
