Using a set of direct numerical simulations (DNS) we investigate the circulation of a buoyancy driven experiment in a circular rotating tank. The initial density structure is a two-layer stable-stratification. The water is densified at 32 points at the upslope side of a circular incline and flows downward as a gravity current before it intrudes to the interior along the interface between the two layers. The water above recirculates to the densification points.When the buoyancy production is lower than the maximal Ekman transport, the gravity current proceeds in the laminar Ekman layer. In the opposite case, the water cascades down the incline in a no-stationary dynamics, turbulent transport becomes important and the boundary layer is thickened. The thermal wind relation applied to the tangential velocity averaged-along-the-slope predicts the density structure averaged-along-the-slope in the domain.When the densified water arrives at the interface it flows along the slope in the cyclonic direction, in a geostrophically adjusted deep boundary current. The distance of the boundary current from the slope is given by inertial overshoot of the Ekman current due to the self advection by the inertia. When this distance is small the boundary current is close to the slope and subject to boundary friction. In the opposite case the boundary current evolves detached from the boundary. The intrusion along the interface, in the (negative) radial direction, is slow, as the intruding distance is proportional to the square-root of time.The recirculation in the upper layer is close to a geostrophic equilibrium. Its quasi-geostrophic evolution is due to the compression of the water column, caused by the gravity and intruding currents, below. This leads to a large-scale anti-cyclonic circulation in the upper layer. When the associated geostrophic surface pressure gradient exceeds the pressured gradient due to the dense water on the slope, the Ekman transport is upslope.A special emphasis is put on the interactions of the three phases of the circulation: gravity-current, intrusion and recirculation. The circulation and the mixing of density and momentum in the gravity current determine the water-mass properties in the deep boundary current. Both determine the recirculation. The recirculation leads to an increasing anti-cyclonic circulation above the gravity current which, through the corresponding surface pressure gradient, reduces and finally blocs the downslope movement in the Ekman layer.