  We use a 43-ks XMM-Newton observation to investigate the nature of sources
first distinguished by a follow-up Chandra observation of the field surrounding
INTEGRAL source IGR J17448-3232, which includes extended emission and a bright
point source previously classified as a blazar. We establish that the extended
emission is a heretofore unknown massive galaxy cluster hidden behind the
Galactic bulge. The emission-weighted temperature of the cluster within the
field of view is 8.8 keV, with parts of the cluster reaching temperatures of up
to 12 keV; no cool core is evident. At a redshift of 0.055, the cluster is
somewhat under-luminous relative to the X-ray luminosity-temperature relation,
which may be attributable to its dynamical state. We present a preliminary
analysis of its properties in this paper. We also confirm that the bright point
source is a blazar, and we propose that it is either a flat spectrum radio
quasar or a low-frequency peaked BL Lac object. We find four other fainter
sources in the field, which we study and tentatively identify. Only one, which
we propose is a foreground Galactic X-ray binary, is hard enough to contribute
to IGR J17448-3232, but it is too faint to be significant. We thus determine
that IGR J17448-3232 is in fact the galaxy cluster up to $\approx$45 keV and
the blazar beyond.
