I recently came across a book about Skefco, the Luton bearing company, during WW2. A couple of pictures from the book, published in 1945, may inspire the terrain builders among us:
LUTON MAIN WORKS: CAMOUFLAGED ENTRANCE TO OFFICES
The principle of the camouflage scheme employed for this quarter-mile long factory was the artificial extension of pavements and roadways of the streets facing the vast front of the factory. How the roadway, complete with "trees", were carried across the rest of the factory is shown elsewhere in these pages.
And, finally, a bonus Bofors gun demonstration/exercise picture from the same book: