Tag object as Terrain
The laTagObjectAsTerrain command turns a piece of geometry into a Terrain. It won't be a true Lands Design Terrain, but plants and other elements will detect it as a terrain and will be projected on top of its upper surface.
This command is available for any Rhino geometry and the Superhatch object.
You can undo this operation by running the laUntagObjectAsTerrain command, available from the Edit area in the Edit panel after selecting the object.