Nearly 40 years after its discovery, the thick disc still posses challenges to our understanding of the Galactic disc: whether it is a distinct component and how its properties like chemistry, star formation history and kinematics relate to those of the thin disc, halo and bulge are current topics of debate. Nevertheless, its importance from the standpoint of disc formation is clear: it contains the oldest most metal-poor stars in the disc, relics from the earliest epochs of disc formation. The current view is that the disc components can be better understood when decomposed as single-age populations or mono-abundance populations as an observational proxy of these. RR Lyrae stars are thus an ideal tracer to study the structure of the old disc, which bypass the considerable difficulty of the observational determination of ages for field stars, as they are unequivocal tracers of old populations (>10 Gyr). In this talk will present recent (pre-Gaia results) for the structure of the old disc traced with RR Lyrae stars and will show the first completeness maps for Gaia DR2 RR Lyrae stars, a key ingredient necessary to update our work with Gaia RR Lyrae. Finally, using Gaia DR2 data we also explore the kinematics of disc RR Lyrae stars and reevaluate the issue of whether the Galactic disc contains RR Lyrae with thin-disc kinematics.