observation - What is in the brightest area of the night sky?

All quoted text in this answer is from image captions in the Wikipedia article on the Milky Way.

360-degree panorama view of the Milky Way (an assembled mosaic of
photographs) by ESO

This magnificent 360-degree panoramic image, covering the entire
southern and northern celestial sphere, reveals the cosmic landscape
that surrounds our tiny blue planet. This gorgeous starscape serves as
the first of three extremely high-resolution images featured in the
GigaGalaxy Zoom project, launched by ESO within the framework of the
International Year of Astronomy 2009 (IYA2009). The plane of our Milky
Way Galaxy, which we see edge-on from our perspective on Earth, cuts a
luminous swath across the image. The projection used in GigaGalaxy
Zoom place the viewer in front of our Galaxy with the Galactic Plane
running horizontally through the image — almost as if we were looking
at the Milky Way from the outside. From this vantage point, the
general components of our spiral galaxy come clearly into view,
including its disc, marbled with both dark and glowing nebulae, which
harbours bright, young stars, as well as the Galaxy’s central bulge
and its satellite galaxies. As filming extended over several months,
objects from the Solar System came and went through the star fields,
with bright planets such as Venus and Jupiter. For copyright reasons,
we cannot provide here the full 800-million-pixel original image,
which can be requested from Serge Brunier. The high resolution image
provided here contains 18 million pixels.

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Here is a schematic map of our POV in the Milky Way galaxy.

Observed (normal lines) and extrapolated (dotted lines) structure of
the spiral arms. The gray lines radiating from the Sun's position
(upper center) list the three-letter abbreviations of the
corresponding constellations.

A "God's view" map of Milky Way as seen from far Galactic North (in
Coma Berenices). The star-like lines center in a yellow dot
representing the position of Sun. The spokes of that "star" are marked
with constellation abbreviations, "Cas" for "Cassiopeia", etc. The
spiral arms are colored differently in order to highlight what
structure belongs to which arm. H II regions are marked as dots
colored in the same color as their spiral arm. They come in three
sizes, measured by the excitation parameter U: small - U > 200 pc cm-2
medium - 200 > U > 110 pc cm-2 large - 110 > U > 70 pc cm-2

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It turns out we are in an arm -- the Orion-Cygnus Arm. The much brighter part of the Milky Way from our POV is in the direction of the galactic center, but the actual nucleus around the supermassive black hole is obscured by dust. If it was visible, it would be quite bright. What we are seeing that is bright is mostly the pseudobulge, or galactic bar formation, in the middle of the galaxy. We are looking at the galactic bar almost end-on, so it resembles a sphere from our POV.