Lumion 10 has included the ability to add heightmap terrain information to come along with Open Street Map building data. Now you can grab full context of each location including cities with iconic mountains or hills all with one click.
can you use the landscape cutter to remove the area with height map you down want to import a large version of your model instead? so the openstreetmap would only be the fat view and everything close building and landscape is part of your model? if that makes sense?