  Context. The ZOA does not allow clear optical observations of extragalactic
sources behind the Milky Way due to the meaningful extinction of the optical
emission of these objects. The observations in NIR wavelengths represent a
potential source of astronomical discoveries supporting the detection of new
galaxies, completing the picture of the large scale structure in this still
little explored area of the sky. Aims. Our aim is to decipher the nature of the
overdensity located behind the Milky Way, in the tile b204 of the VVV survey.
Methods. We studied an area of six arcmin around a galaxy concentration located
at l = 354.82{\deg} and b = -9.81{\deg}. We selected five galaxies taking into
account the source distribution on the sky, in order to optimise the requested
time for the observations, and we obtained the spectra with Flamingos 2
long-slit spectrograph at Gemini South 8.1-meter telescope. To identify and
characterise the absorption features we have fitted the galaxies underlying
spectrum using the starlight code together with the IRTF stellar library. In
addition, the spectroscopic findings are reinforced using complementary
photometric techniques such as red-sequence and photometric redshift
estimation. Results. The mean spectroscopic redshift estimated from the NIR
spectra is z = 0.225 +- 0.014. This value presents a good agreement with that
obtained from photometric analysis, photoz = 0.21 +- 0.08, and the probability
distribution function of the galaxies in the studied region. Also, the
red-sequence slope is consistent with the one expected for NIR observations of
galaxy clusters. Conclusions. The redshifts obtained from both, photometric and
spectroscopic techniques are in good agreement allowing the confirmation of the
nature of this structure at z = 0.225 +- 0.014, unveiling a new galaxy cluster,
VVVGCl-B J181435-381432, behind the Milky Way bulge.
