  The kinematics, shaping, density distribution, expansion distance, and
ionized mass of the nebula Hen 2-104, and the nature of its symbiotic Mira are
investigated. A combination of multi-epoch HST images and VLT integral field
high-resolution spectroscopy is used to study the nebular dynamics both along
the line of sight and in the plane of the sky. These observations allow us to
construct a 3-D spatio-kinematical model of the nebula, which together with the
measurement of its apparent expansion in the plane of the sky over a period of
4 years, provides the expansion parallax for the nebula. The integral field
data featuring the [S{\sc ii}] $\lambda\lambda$671.7,673.1 emission line
doublet provide us with a density map of the inner lobes of the nebula, which
together with the distance estimation allow us to estimate its ionized mass. We
find densities ranging from n$_e$=500 to 1000 cm$^{-3}$ in the inner lobes and
from 300 to 500cm$^{-3}$ in the outer lobes. We determine an expansion parallax
distance of 3.3$\pm$0.9 kpc to Hen 2-104, implying an unexpectedly large
ionized mass for the nebula of the order of one tenth of a solar mass.
