Dolly Parton is putting some more big curves into her Dollywood theme park. And some big dips and spins, too.

Tennessee's top tourist draw will add a $17.5 million steel roller coaster called "Mystery Mine" in 2007, the country singer and actress announced Friday. It's the biggest single capital investment in the park's 21-year history.

"I've had to keep my big mouth shut about the Mystery Mine, but I can tell you now," Dolly said. "It's the most exciting thing to come out of these hills in a long, long time."

The coaster, with the theme of an abandoned coal mine, will take riders on a 2 1/2-minute trip featuring a weightless inversion known as a "heart-line roll," a double inversion known as a "rollover loop" and a kind of half-loop climb, turn and plunge perfected by combat pilots in World War I.

The 1,811-foot coaster will cover an acre and join Dollywood's other major coaster, the wooden Thunderhead.