  The construction of the H.E.S.S. (High Energy Stereoscopic System), a
superior system of four 12 m imaging atmospheric Cherenkov telescopes, has been
completed recently in the Namib desert close to Windhoek, at 1800 m above sea
level. This new generation of ground-based gamma-ray detectors has an energy
threshold of about 100 GeV in observations at zenith and a sensitivity of about
1% Crab flux for a point-like gamma-ray source. Such high sensitivity was
achieved due to 0.1 degree angular resolution, as well as, severe cosmic ray
background rejection acquired from multi-fold imaging of individual atmospheric
showers. In addition H.E.S.S. has a rather good energy resolution of 15%.
H.E.S.S. has been taking routine observations of the gamma-ray sources since
December 2003. The outstanding physics results achieved with H.E.S.S. already
in a first year of its exploitation strongly encourage further development of
imaging atmospheric Cherenkov technique for high-quality gamma-ray
observations, which is basically driven by father reduction of the energy
threshold of a forthcoming major future gamma-ray detector. Here we are dealing
with such a detector. Basic results on performance and sensitivity for a single
stand-alone 30 m imaging atmospheric Cherenkov telescope, as well as for a
system of two and five telescopes, are discussed here.
