  We used a combination of public RR Lyrae star catalogs and a Bayesian
methodology to derive robust structural parameters of the inner Halo (<25 kpc)
and Thick Disc of the Milky Way. RR Lyrae stars are an unequivocal tracer of
old metal-poor populations, for which accurate distances and extinctions can be
individually estimated and so, are a reliable independent means of tracing the
population of the old high-[\alpha/Fe] disc usually associated to the Thick
Disc. In particular, the chosen RR Lyrae sample spans regions at low galactic
latitude toward the anti-center direction, allowing to probe the outermost
parts of the disc. Our results favour a Thick Disc with short scale height and
short scale length, $h_z=0.65_{-0.05}^{+0.09}$ kpc, $h_R=2.1_{-0.25}^{+0.82}$
kpc, for a model in which the inner Halo has a constant flattening of
$q=0.90_{-0.03}^{+0.05}$ and a power law index of $n=-2.78_{-0.05}^{+0.05}$.
Similar short scales for the Thick Disc are also found when considering an
inner Halo with flattening dependent on radius. We also explored a model in
which the Thick Disc has a flare and, although this is only mildly constrained
by our data, a flare onset in the inner $\sim11$ kpc is highly disfavoured.
