  We provide a group theory approach to coherent states describing quantum
space-time and its properties. This provides a relativistic framework for the
metric of a Riemmanian space with bosonic and fermionic coordinates, its
continuum and discrete states, and a kind of {\it"quantum optics"} for the
space-time. {\bf New} results of this paper are: (i) The space-time is
described as a physical coherent state of the complete covering of the SL(2C)
group, eg the Metaplectic group Mp(n). (ii) (The discrete structure arises from
its two irreducible: $\textit{even}$ $(2n)$ and $\textit{odd}$ $(2n\;+\;1)\;$
representations, ($n = 1,\, 2, \,3\,...$ ), spanning the complete Hilbert space
$\mathcal{H} = \mathcal{H}_{odd}\oplus \mathcal{H}_{even}$. Such a global or
{\it complete} covering guarantees the CPT symmetry and unitarity. Large $n$
yields the classical and continuum manifold, as it must be. (iii) The coherent
and squeezed states and Wigner functions of quantum-space-time for black holes
and de Sitter, and (iv) for the quantum space-imaginary time (instantons),
black holes in particular. They encompass the semiclassical space-time
behaviour plus high quantum phase oscillations, and notably account for the
classical-quantum gravity duality and trans-Planckian domain. The Planck scale
consistently corresponds to the coherent state eigenvalue $\alpha = 0$ (and to
the $n = 0$ level in the discrete representation). It is remarkable the power
of coherent states in describing both continuum and discrete space-time. The
quantum space-time description is {\it regular}, there is no any space-time
singularity here, as it must be.
