In Montrose County, Colorado, an incredible feat of mining engineering clings to sheer canyon walls above the Dolores and San Miguel rivers. Built in the 1880s, the Hanging Flume carried the water used to extract the fine gold from placer deposits. The flume has captivated historians and tourists alike, but no one has been able to determine exactly how it was built in just a few years in such a remote and inhospitable location.