ParametricPlot[{r Cos[θ],r Sin[θ]},{θ,0,2π},{r,1,2+Cos[θ]},PlotStyle->{LightBlue,Opacity[0.2]},PlotPoints->30]

Show[Graphics[{Blue,Thick,Circle[{0,0},2]}],ParametricPlot[{r Cos[θ],r Sin[θ]},{θ,0,2π},{r,0,2Cos[θ]},PlotStyle->{LightBlue,Opacity[0.2]},PlotPoints->30,BoundaryStyle->{Thick}]]

ParametricPlot3D[{{r Cos[θ],r Sin[θ],(r^2)},{r Cos[θ],r Sin[θ],8-(r^2)}},{θ,0,2π},{r,0,2},PlotStyle->Directive[White,Specularity[White,20],Opacity[0.8]]]

Plot3D[Exp[-(x^2)-(y^2)],{x,-2,2},{y,-2,2},PlotStyle->Directive[LightGray,Specularity[White,20],Opacity[0.8]]]