At my FLGS, a friend of mine spearheaded the construction of this river battle board. Its meant to simulate the "Barrels out of Bond" scenario from the latest LotR miniature game and The Desolation of Smaug.
It's 4'x6', and each layer is made of plywood. The river banks themselves are constructed from tree bark. The bridge, a type of resin. The island in the middle is movable, as are the trees and the ruins. He's bought the figures of the dwarves and Bilbo made specifically for this scenario from the company-that-shall-not-be-named.
He's also has a dock in the works, along with a section of bridge that spans up to the highest area in the foreground.
It can even be removed and replace with different battle boards that the store has--but this the most intricate made thus far.
I'm already thinking of all kinds of scenarios for both wargaming and roleplaying.