  Color centers in diamond, among them the negatively-charged germanium vacancy
(GeV$^-$), are promising candidates for many applications of quantum optics
such as a quantum network. For efficient implementation, the optical
transitions need to be coupled to a single optical mode. Here, we demonstrate
the transfer of a nanodiamond containing a single ingrown GeV- center with
excellent optical properties to an open Fabry-P\'erot microcavity by
nanomanipulation utilizing an atomic force microscope. Coupling of the GeV-
defect to the cavity mode is achieved, while the optical resonator maintains a
high finesse of F = 7,700 and a 48-fold spectral density enhancement is
observed. This article demonstrates the integration of a GeV- defect with a
Fabry-P\'erot microcavity under ambient conditions with the potential to extend
the experiments to cryogenic temperatures towards an efficient spin-photon
platform.
