The Argo Mill and Tunnel is the giant red gold mill that climbs the hillside above Clear Creek in Idaho Springs. Built in 1913 at the mouth of a tunnel bored more than four miles into the mountains, it processed millions of dollars in gold ore, and today guided tours lead you through the mill and end with a chance to pan for real gold.

Idaho Springs is where the Colorado Gold Rush began: in January 1859, George Jackson found placer gold where Chicago Creek meets Clear Creek. As the mines around Central City, then known as “the richest square mile on earth,” went deeper, groundwater flooded the shafts. The fix was the Newhouse Tunnel, later renamed the Argo Tunnel, an adit driven 4.16 miles into the mountain that drained nearly 300 miles of mine workings and served more than 100 mines. It took the better part of two decades to finish. The Argo Mill was completed at the tunnel mouth in 1913 to process lower-grade ore on site before it was shipped by rail to the Denver Mint, and it ran on alternating current before Denver itself was electrified. In 1943, mine workings collapsed into the tunnel and caused a flood that ended milling for good. James Maxwell bought the mill in 1977 and preserved it for tours, and the current owners bought it in 2016. The site is listed on the National Register of Historic Places.

The guided mill tour follows the path of the ore from the tunnel portal down through the mill, where much of the original equipment from the early 1900s is still in place. Guides explain the people, technology and business behind one of the most advanced mills of its day, and the tour ends with a gold panning lesson using real ore, so everyone takes home a little gold. Plan on about an hour and a half with panning. The Argo is now part of the Mighty Argo, which also runs a cable car and lift-served mountain biking from the same base, plus a Mercantile with souvenirs and Colorado history books. Idaho Springs is about 30 miles west of Denver on I-70, so the Argo pairs easily with lunch downtown or a soak at the town’s hot springs.

Check the Mighty Argo Plan Your Visit page for current hours, tickets and the event calendar. This fall, the Mighty Argo is running a sale with $10 off cable car tickets and mountain biking, and its Gold Package bundles the cable car, mill tour and all-day parking for $59.95 per adult.