protected areas of Vietnam
... that Phong Nha-Ke Bang National Park, one of the protected areas of Vietnam, has the largest cave in the world?
... that <a class="mw-redirect" href="./Phong_Nha-Ke_Bang_National_Park" id="mwARo" rel="mw:WikiLink" title="Phong Nha-Ke Bang National Park">Phong Nha-Ke Bang National Park</a>, one of the <b id="mwARs"><a href="./Protected_areas_of_Vietnam" id="mwARw" rel="mw:WikiLink" title="Protected areas of Vietnam">protected areas of Vietnam</a></b>, has the largest cave in the world?