The original email containing pictures of the real thing said the road is in Bolivia, and the name means "road of death". However, later checking indicates that it is actually Gualiang Tunnel, which is near Mount Taihang, near Beijing, China. One of the early sites containing this images is on the Skycraper forum. In turn, that points to a Chinese-language site that includes many more pictures of the area. I've taken the sign image from there.
The first LEGO planning for this project had the cliff twice as high and nearly twice as long. That was completely impractical, so this new version was planned out. The cliff only needs one side of a "mountain", so the other side was planned as simple green slopes. It got a bit more complicated.