OK, Joshua, here we go:
Yes, it is a painting of a landscape at the end of a tunnel (of plants). The people watching the painting are real on a visiting tour (regular visitors don't come that close, you should watch the scene from the point i was standing).
Symbolising the convergence of nature and culture - the park becoming a painting and vice versa.
The whole park is full of such plays: Ruins, statues a mosque, a water plant etc. all 'faked' for the pleasure of the mastermind, Carl Theodor, the Kurfürst.
Cheers
Werner