This isn't exactly what you had in mind as a "second course," but in the US I'd mention Spyglass in Pebble Beach. I think that Spyglass is a terrific course, and while not ignored, it is downgraded by being next to the Pebble Beach course. I'm sure if it were standing alone, it would be more respected.
I only think of it in the second course sense, because the story is (which I can't verify) that Spyglass was being talked about as a PGA Tournament course, and the PGA said (reportedly), "We're not going to take the second course, when you give your number one course to the USGA."
In terms of difficulty, variety and playability, it is the equal of Pebble Beach--lacking only in beauty (a bit) and prestige.