CAVE CITY, Ky. (AP) — Officials say the world’s longest cave system has added 8 miles to its length. Mammoth Cave National Park said in a statement on Saturday that the additional mileage was mapped and documented by the Cave Research Foundation. The statement said that brings the total length of the cave system in south-central Kentucky to 420 miles. The announcement highlighted the park’s recognition of National Day of Service and its longtime partnership with the nonprofit foundation. Volunteers with the foundation have worked with the park for decades to map and document Mammoth Cave.