PGK Art: The Bridge That Was Central Railroad of New Jersey abandoned Turn Hole Tunnel in Glen Onoko, Pennsylvania — the original alignment of the Lehigh & Susquehanna Railroad at Glen Onoko passed through the mountain in a short tunnel whose west bore opened onto the river; in 1912, the CNJ mainline was realigned around the west slope of the mountain; the old mainline at the west end of Turn Hole Tunnel opened onto CNJ bridge No. 120/28 at the Lehigh River; after 1912 the old mainline was used as a passing siding until its abandonment in July 1956.