Autodesk Revit Architecture

[#1]

How do you control the bottom depth of a toposurface?  I have a structure with a basement and the "Earth" stops at the top of the footings so that my details show the footings floating in space!!

[#2 · Accepted solution]

Massing and Site > Model Site - click on the small arrow on the right corner - Site Settings dialog opens >Section Graphics > Elevation of Poche Base 

It is shown only in SECTIONS.  If you want to show it in an elevation move the elevation line so to cut the terrain

[#3]

Thanks.  That did it.