LOUISVILLE, Ky. (AP) — A colossal cave system in Kentucky that's known as the longest in the world has reached 400 miles.
Mammoth Cave recently added 10 miles to its explored underground length, pushing it past the 400-mile mark, the National Park Service said.
The expansion is thanks to several "incremental additions to many parts of the cave rather than a single major discovery," said Charles Fox, president of the Cave Research Foundation, which enlists volunteers to help explore the cave. The park service made the announcement Friday.
Each year, the popular destination in south-central Kentucky attracts enthusiasts who spend thousands of hours scouring the winding underground limestone caverns. Fox said in a statement that the group has resurveyed sections of the cave to produce maps with better detail and also added previously unexplored passages.
Roger Brucker, an author who began exploring the cave in the 1950s, said the new milestone is a payoff for all the explorers who have helped find new connections over the decades. Brucker, 83, said the explored length was around 40 miles when he began going underground.
"The fun of it to me is finding that the system is connected and how it is connected," he said Wednesday. "Generally, it involves crawling through water, wading through water."