  We present a 2.5-dimensional magnetohydrodynamic simulation of a
systematically rotating prominence inside its coronal cavity using the
open-source \texttt{MPI-AMRVAC} code. Our simulation starts from a
non-adiabatic, gravitationally stratified corona, permeated with a sheared
arcade magnetic structure. The flux rope (FR) is formed through converging and
shearing footpoints driving, simultaneously applying randomized heating at the
bottom. The latter induces a left-right asymmetry of temperature and density
distributions with respect to the polarity-inversion line. This asymmetry
drives flows along the loops before the FR formation, which gets converted to
net rotational motions upon reconnection of the field lines. As the thermal
instability within the FR develops, angular momentum conservation about its
axis leads to a systematic rotation of both hot coronal and cold condensed
plasma. The initial rotational velocity exceeds $60\ \mathrm{km\ s^{-1}}$. The
synthesized images confirm the simultaneous rotations of the coronal plasma
seen in 211 and 193 \AA\ and condensations seen in 304 \AA. Furthermore, the
formation of the dark cavity is evident in 211 and 193 \AA\ images. Our
numerical experiment is inspired by observations of so-called giant solar
prominence tornadoes, and reveals that asymmetric FR formation can be crucial
in triggering rotational motions. We reproduce observed spinning motions inside
the coronal cavity, augmenting our understanding of the complex dynamics of
rotating prominences.
