Lime Rock - The Mountain Circuit by Brent Adams for Grand Prix Legends
When Jim Vaill, whose family owned the land that Lime Rock was situated on, was laying out the 1.53-mile track in 1956, he envisioned a 1.5-mile addition to the main course which would extend the front straight, rise up in the hills behind Big Bend and the Left, then plunge down to rejoin the existing track after the exit of the Hook.
Vaill got as far as bulldozing a "rough cut" of the Mountain Circuit, as it was called (its traces are still visible today; you can hike the trail), and it's in an "artist's conception" of the track prepared by industrial designer Raymond Loewy, but the MC was never built, for a variety of reasons, among them cost...and the lack of enough corner workers to cover the whole course.
one of the great might-have-beens in U.S. racing. The 2.93-mile Mountain Circuit is presented as it might have looked in 1957, when the main track first opened to the public on the weekend of April 27-28.
I converted and updated this track in 2012 for Rf1, to the best of my knowledge it never ran in Rf2.