Hot Sulphur Springs, United States. A 13-mile long ten-foot wide water tunnel runs under Rocky Mountain National Park, from one end to the other, crossing 3,700 feet under the Continental Divide. It is the fulcrum of a network of trans-basin, trans-divide reservoirs and pipelines known as the Colorado-Big Thompson project, built by the U.S. Bureau of Reclamation, and completed in 1947, at a cost of $160 million.