How to place Contourf at a new height?

I have the following plot and the Contourf.

By default, Contourf will always be generated at height Z = 0 i.e. the horizontal plane. I would like to shift Contourf to height Z = -2, this is so the contour will be placed under the graph of my function. How do I achieve this?

Code:

x = linspace(0,1,1000);
y = linspace(0,1,1000);
[X,Y] = meshgrid(x,y);
Z = -X.^2 - Y.^2;
mesh(X,Y,Z)
box on
hold on
contourf(X,Y,Z)

Answer 1

[Star Strider]

This seems to work:

x = linspace(0,1,1000);
y = linspace(0,1,1000);
[X,Y] = meshgrid(x,y);
Z = -X.^2 - Y.^2;
mesh(X,Y,Z+2)
box on
hold on
contourf(X,Y,Z+2)
zt = get(gca, 'ZTick');
set(gca, 'ZTick',zt, 'ZTickLabel',zt-2)
view([15  35])

Change the view arguments to the orientation you want.

A likely better option is Customizing contour plots part 2 (link).