Water and time entwined to create one of the most acoustically pure natural spaces on earth, the Volcano Room at Cumberland Caverns in McMinnville, Tenn. This world-renowned venue is celebrated today as Bluegrass Underground, a monthly bluegrass concert series featuring some of the greatest musicians in the region in an intimate subterranean setting.

If you go

What: Bluegrass Underground at Cumberland Caverns, amusical venue located 333 feet underground, featuring bluegrass, Americana, roots, gospel and old-time country performances by renowned regional musicians.

Where:McMinnville, Tenn. (located 1.25 hours north of Chattanooga)

For more information:http://www.bluegrassunderground.com

Where to eat:Teddy Jones, general manager at Cumberland Caverns, recommends a stop at Gary & Gail’s Pit Stop off Highway 8 in McMinnville: “It’s a locally owned mom-and-pop restaurant, and they have great burgers, barbecue and fish,” Jones said.

The Volcano Room, with its natural acoustics, was destined for musical greatness. Located 333 feet below the surface of Cardwell Mountain in Cumberland Caverns, the room was uniquely formed at the conflux of two ancient underground rivers. Water and whirlpools carved the ceiling and walls in a way that, today, wondrously carries the sound of the region’s native music. The room resonates at 2 frequencies, which means that experiencing live music there is akin to attending a concert inside a recording studio.

Each month, Bluegrass Underground features musical performances that highlight bluegrass, Americana, gospel, roots and old-time country music in a setting like no other on earth.

“The sound just kind of envelopes you,” Teddy Jones, general manager at Cumberland Caverns, said. “The shape of the room, the ceiling and walls that were etched out by water over millions of years, create a room with no echo. Because of that, it is a real treat for the audience, as well as the musicians.”

Bluegrass Underground launched in August 2008 and has featured some of the biggest acts in bluegrass music, from Entertainer of the Year award-winners to members of the Bluegrass Hall of Honor. Vince Gill, Ricky Skaggs, Charlie Louvin, The Civil Wars and Bobby Osborne of the Osborne Brothers have all played the stage in the Volcano Room.

The show has a cult following, according to Jones, and can be heard on Saturdays at 5 p.m. CST on WSM 650AM in Nashville, right before the Grand Ole Opry. The show can also be watched online at http://www.wsmonline.com. Two seasons of concerts can also be seen nationwide on PBS, which has brought in a broader audience from across the country.

“It has been amazing to see the show grow,” Jones said. “As soon as it hit on PBS last fall, we have sold out just about every show.”

Cumberland Caverns-one of Tennessee’s largest caves-was discovered in 1810 by Aaron Higgenbotham while he was surveying the nearby Chickamauga Trail.

According to legend, Higgenbotham dropped his torch over a ledge and was trapped inside the cave for three days. When he was found, it is said that his hair was white from fear.

The cave is set along the path of the Trail of Tears, when the Cherokee were forcibly removed from their lands in the Southeast. It was also a source of saltpeter (the main ingredient of gunpowder) and operated as a saltpeter mine during the War of 1812 and the Civil War.

Cumberland Caverns, which opened to the public in 1956, also shares its space with a small population of bats, which occasionally can be spotted in the Volcano Room, Jones said.

“A couple of times, a few bats have flown out over the concert, which always thrills the crowd,” Jones said. “They don’t seem to be bothered by the music, though.”

Typically, one-third of the Bluegrass Underground crowd takes a tour of the cave prior to the concert, which gives Jones and his staff the opportunity to talk about cave conservation and bats with people who might not normally visit.

“I love this cave and want to share it with other people,” Jones said. “The music has given us a much larger audience to talk about cave conservation and bats with.”

Bluegrass Underground will present “An East Nashville Christmas” on Saturday, Dec. 8 from 1 to 4 p.m. The show is part of a holiday-themed compilation album and concert series created by a coalition of 75 Nashville-based artists and musicians to raise funds and awareness for National Health Care for the Homeless. Performances will include Mike Farris, Christian Sedelmyer and Rachel Baiman, Jeff and Vida, Todd Grebe and Cold Country, Grace Adele, Derek Hoke and Jen Duke, Julie Lee and The Danberrys.

The best way to ensure a ticket (shows often sell out) is to purchase it online at www.bluegrassunderground.com, according to Jones. Seating is general admission, but the intimate amphitheater environment guarantees a good seat from anywhere within the Volcano Room. The tour-and-concert package offers the added advantage of early seating.

Jenni Frankenberg Veal enjoys writing about the natural world and the people who work to protect it. This Christmas, she is asking Santa for a book publishing deal and some new Chaco sandals. Visit her blog at YourOutdoorFamily.com.