The East Bay Regional Park District began acquiring land for Black Diamond Mines Regional Preserve in the early 1970s. Today, most of the mining district is within the Preserve’s nearly 5,717 acres. The area is an ideal location for hiking, picnicking and nature study. Naturalists conduct a variety of programs relating the Preserve’s natural and historic resources. One and one half hour-long, advance-reservation tours are offered seasonally — see website for details.