AnimalsMind-BlowingAn underground fire in Australia has been burning for approximately 6,000 years, making it the world's oldest known coal fire.10712k
HistoryMind-BlowingIn 1963, a man found a mysterious room behind a wall in his home that lead to a huge underground city that once housed up to 20,000 people, complete with schools, livestock pens, and food stores, dating back over a millennium.689k
PlacesWeirdThe largest underground hotel suite in the world is located 21 stories below the surface in Arizona's Grand Canyon Caverns. The Cavern Suite sits in a 345-million-year-old cave and costs $1,000 per night.72k