Abandoned mines have been featured in many horror movies, and for good reason. They can be both dangerous and scary. But, even if you've wisely decided not to explore the spooky old mines that you know about, there may be dozens more around your area about which you're unaware. To find out more about abandoned mine lands and what's being done to make them safe, see this page from the Bureau of Land Management:
And, if you see a "Keep Out" sign, think back to the fate of the people in those horror movies and please do what it says.