Black Diamond Mines Regional Preserve is a scenic park located in Contra Costa County, California. It covers over 6,000 acres and features rolling hills, open spaces, and remnants of historic coal and clay mining operations. Visitors can explore various trails that offer stunning views of the surrounding landscape. The preserve is home to diverse wildlife and plant species, making it a great spot for nature enthusiasts. Additionally, the park includes several historic sites, such as the Black Diamond Mine and the Newman Mine, which provide insight into the area's mining history and heritage.