STL Files
From charlesreid1
Viewing STL Files
ParaView
ParaView: http://www.paraview.org/download/
FreeCAD
FreeCAD binary files: https://github.com/FreeCAD/FreeCAD/releases
Visualizing Map Shapefiles
I downloaded contour elevation data for the Seattle area, which was contained in a zip file called Elev_322166_Seattle_E_1X1.zip.
Unzipping results in a pile of files of various formats:
When you first open FreeCAD, you'll see this:
If you do a File > Open, you'll see lots of available file formats: