Michael Locke:
Penn's Cave, Centre Hall, Pennsylvania
Michael Locke:
Crystal Lake, Mammoth Cave
Michael Locke:
Chinese Temple, Mammoth Cave
Michael Locke:
Ruins of Karnak, Mammoth Cave
Michael Locke:
Mammoth Dome, Mammoth Cave National Park
Michael Locke:
Hall of Dreams, Ruby Falls, Lookout Mountain, Tennessee
Michael Locke:
Polar Caves Park, Rumney, New Hampshire
Michael Locke:
Drachenhöhle
Michael Locke:
Cathedral Hall, Grand Canyons of Virginia
Michael Locke:
Grand Ballroom, Grand Caverns of Virginia
Michael Locke:
Grand Ballroom, Grand Caverns of Virginia 2
Michael Locke:
Cave of the Winds, Colorado
Michael Locke:
Alum Cave Trail, Great Smoky Mountains National Park
Michael Locke:
Rushmore Cave
Michael Locke:
Meramec Caverns
Michael Locke:
Ruby Falls, Lookout Mountains Caverns
Michael Locke:
Mamoth Cave National Park
Michael Locke:
Cloudland Canyon State Park
Michael Locke:
Empress Column, Luray Caverns
Michael Locke:
Saracens Tent, Luray Caverns
Michael Locke:
Skyline Caverns
Michael Locke:
Sarecens Tent, Luray Caverns
Michael Locke:
Skyline Caverns, Front Royal, Virginia
Michael Locke:
Colossal Caves
Michael Locke:
Cave of Altamira
Michael Locke:
Ruby Falls
Michael Locke:
Carlsbad Caverns National Park
Michael Locke:
Miguel Hidalgo Underground Street, Guanajuato, Mexico
Michael Locke:
Miguel Hidalgo Street Underground, Guanajuato, Mexico
Michael Locke:
The Crystal Caves, Bermuda
