  We study the three-dimensional structure of the Milky Way using 65,981 Mira
variable stars discovered by the Optical Gravitational Lensing Experiment
(OGLE) survey. The spatial distribution of the Mira stars is analyzed with a
model containing three barred components that include the X-shaped boxy
component in the Galactic center (GC), and an axisymmetric disk. We take into
account the distance uncertainties by implementing the Bayesian hierarchical
inference method. The distance to the GC is $R_0 = 7.66 \pm 0.01
\mathrm{(stat.)} \pm 0.39 \mathrm{(sys.)}$ kpc, while the inclination of the
major axis of the bulge to the Sun-GC line-of-sight is $\theta = 20.2^\circ \pm
0.6^\circ \mathrm{(stat.)} \pm 0.7^\circ \mathrm{(sys.)} $. We present, for the
first time, a detailed three-dimensional map of the Milky Way composed of young
and intermediate-age stellar populations. Our analysis provides independent
evidence for both the X-shaped bulge component and the flaring disk (being
plausibly warped). We provide the complete dataset of properties of Miras that
were used for calculations in this work. The table includes: mean brightness
and amplitudes in nine photometric bands (covering a range of wavelength from
0.5 to 12 $\mu$m), photometric chemical type, estimated extinction, and
calculated distance with its uncertainty for each Mira variable. The median
distance accuracy to a Mira star is at the level of $6.6\%$.
