Denver Mining Club Tour of the “Richest Square Mile on Earth. On Monday, September 12, we’ll meet at noon at the Central City Visitor Center, 103 Eureka Street, Central City. Then travel in your own vehicle or carpool (2-WD is fine) on a guided, ~3-hour tour to various sites, including Gregory Diggins, Nevadaville, Russell Gulch, and the Chaffee mine. Bring water and lunch. Cost: $10 for Chaffee mine ($36 to purchase a Chaffee mine silver bar), plus tip of your choice for your tour guide.