(Associated Press) In decades of ceaseless touring, bluegrass icon Ralph Stanley thought he’d played in every venue imaginable.

Then he got an invite to play a “Bluegrass Underground” show earlier this year.

“It’s a good day to be here,” Stanley told a crowd of several hundred fans, some of whom hung from rocky ledges around the rim of the Volcano Room 333 feet below ground. “I hope we can get out. I’ve been playing for 65 years now, and I’ve never played in a cave.”

In a few short years, “Bluegrass Underground” and the Volcano Room at Cumberland Caverns near McMinnville, Tenn., have become a hot destination for top bluegrassers and acoustic musicians around the country. And a new weekly show on PBS should help raise the profile of one of the nation’s most unique concert spaces even more.