  We discuss black hole quantization in the Wheeler-DeWitt approach. Our
consideration is based on a detailed investigation of the canonical formulation
of gravity with special considerations of surface terms. Since the phase space
of gravity for non-compact spacetimes or spacetimes with boundaries is
ill-defined unless one takes boundary degrees of freedom into account, we give
a Hamiltonian formulation of the Einstein-Hilbert-action as well as a
Hamiltonian formulation of the surface terms. It then is shown how application
to black hole spacetimes connects the boundary degrees of freedom with
thermodynamical properties of black hole physics. Our treatment of the surface
terms thereby naturally leads to the Nernst theorem. Moreover, it will produce
insights into correlations between the Lorentzian and the Euclidean theory.
Next we discuss quantization, which we perform in a standard manner. It is
shown how the thermodynamical properties can be rediscovered from the quantum
equations by a WKB like approximation scheme. Back reaction is treated by going
beyond the first order approximation. We end our discussion by a rigorous
investigation of the so-called BTZ solution in 2+1 dimensional gravity.

General Relativity and Quantum Cosmology