  Nova eruptions occur in cataclysmic variables when enough material has been
accreted onto the surface of the white dwarf primary. As a consequence, the
material that has been accumulated until then is expelled into the interstellar
medium, forming an expanding nova shell around the system. Understanding the
physical process that shapes the morphology of nova shells is essential to
fully comprehend how the ejection mechanism operates during nova eruptions.
Because of its closeness and age, the nova shell around the classical nova RR
Pic (Nova Pic 1925) is an ideal target for studying the evolving morphology of
nova shells. In this work, we present an IFS study of the RR Pic nova shell,
with a particular emphasis on the extraction of the 3D morphology of the shell.
The nova shell was observed by the Multi-Unit Spectroscopic Explorer (MUSE)
instrument placed at the ESO-VLT. The MUSE datacube confirms the presence of
the nova shell in H$\rm\alpha$, H$\rm\beta$ and [OIII], and very faintly in
[NII]. A comparison with previous observations suggests that the shell
continues in its free-expansion phase but with the different parts of the shell
apparently expanding at different rates. The data analysis corroborates the
previous vision that the shell is composed of an equatorial ring and polar
filaments. At the same time, the new data also reveal that [OIII] is confined
in gaps located in the tropical regions of the shell where no Hydrogen is
observed. The flux measurements indicate that ~99% of the shell flux is
confined to the equatorial ring, while the polar filaments show a flux
asymmetry between the NE and SW filaments. We have estimated the mass of the
shell to be ~5x10$^{-5}$M$_\odot$. From the analysis of the 3D-extracted data,
we determine that the ring structure extends ~8,000 au from the central binary,
and has a position angle of ~155 deg and an inclination of ~74 deg.
