  We investigate the large-scale circulation (LSC) of turbulent
Rayleigh-B\'enard convection in a large box of aspect ratio $\Gamma =32$ for
Rayleigh numbers up to $Ra=10^9$ and at a fixed Prandtl number $Pr=1$. A
conditional averaging technique allows us to extract statistics of the LSC even
though the number and the orientation of the structures vary throughout the
domain. We find that various properties of the LSC obtained here, such as the
wall-shear stress distribution, the boundary layer thicknesses and the wind
Reynolds number, do not differ significantly from results in confined domains
($\Gamma \approx 1$). This is remarkable given that the size of the structures
(as measured by the width of a single convection roll) more than doubles at the
highest $Ra$ as the confinement is removed. An extrapolation towards the
critical shear Reynolds number of $Re_s^{\textrm{crit}} \approx 420$, at which
the boundary layer (BL) typically becomes turbulent, predicts that the
transition to the ultimate regime is expected at $Ra_{\textrm{crit}} \approx
\mathcal{O}(10^{15})$ in unconfined geometries. This result is in line with the
G\"ottingen experimental observations. Furthermore, we confirm that the local
heat transport close to the wall is highest in the plume impacting region,
where the thermal BL is thinnest, and lowest in the plume emitting region,
where the thermal BL is thickest. This trend, however, weakens with increasing
$Ra$.
