Mystery Mine coaster opens at Dollywood in 2007. Country singer Dolly Parton is bringing new thrills to her Dollywood theme park. The new Mystery Mine rollercoaster opens in 2007 at a cost of $17.5 million, the biggest single capital investment in the Tennessee park's 21 years. "I’ve had to keep my big mouth shut about the Mystery Mine, but I can tell you now," Parton said Friday. "It’s the most exciting thing to come out of these hills in a long, long time." The new ride, themed after an abandoned coalmine, will thrill visitors with several inversions, climbs and turns on its 2 1/2-minute trip. It joins the park's other rollercoaster Thunderhead.