Boulder Cave: Just outside of Naches in the Mount Rainier area you can explore this cave that was formed millions of years ago from volcanic activity, though it's now home to dozens of Pacific western big-eared bats!
The Hoosac Tunnel - It's said that around 200 men died in the construction of this tunnel from accidents to murder. It is believed that some of these men haunt the tunnel. Reported activity includes apparitions and strange lights.
Hoosac Tunnel Built underneath 5 miles of the Berkshire Mountains of Massachusetts, this haunted abode has been dubbed the Bloody Pit. From what I can recall, it had seen nearly 200 deaths during its 24-year construction; the deaths being caused by fires, explosions, and structural collapse. Murder also had its part in the history of the tunnel's construction.