Introduction
The Spiral Tunnels are two 270-degree looping railway tunnels bored through Cathedral Mountain and Mount Ogden in Yoho National Park's Kicking Horse Pass, British Columbia. Completed in 1909 and designed by J.E. Schwitzer, they were engineered to halve the dangerous grade of the old 'Big Hill' route, allowing CPKC trains to spiral inside the mountains rather than descend steeply. Visitors can watch trains loop through the tunnels from established viewpoints along the Trans-Canada Highway between Field and the pass summit.