Sen. Mitch McConnell and Rep. Brett Guthrie both filed the Mammoth Cave National Park Boundary Adjustment Act on Thursday.

In a world where we can examine just about every part of the planet's surface with Google Maps, it sometimes feels ... Rick Steves' favorite cave system is a hidden gem tucked away in Slovenia.

No one knows how big the underside is. More than 365 miles of the five-level cave system have been mapped, and new caves are continually being discovered. Two layers of stone underlie Mammoth's ...