September 11, 2015 4:30 pm The Underground Behemoth: Louisville Mega Cavern Audrina explores the 4,000,000 square feet that is Louisville Mega Cavern: BMX biking, the ropes course and ziplining… all underground. US & World Videos 2:08 Travis Kelce calls Taylor Swift his ‘significant other' as they attend Charity Gala Date Night 1:04 Hunter Biden plans to sue Fox News 1:17 Student loan forgiveness: Deadline to consolidate loans is April 30 0:59 Runaway zebras corralled in Washington state; one still missing 1:40 Charlie Puth reacts to Taylor Swift's ‘The Tortured Poets Department' name-drop