In 1942 it was targeted by the Nazis as part of their intelligence plan Operation Pastorius. Thankfully the plan never came to fruition. It opened almost a century before World War II as part of the Norfolk Southern Railroad. It measures 2,375 feet long and 1,300 feet in diameter, winding its way around a reservoir. Today it is a popular tourist attraction, complete with an observation park, a visitor center, a 198-step staircase, and a 288-foot funicular.