Great Onyx Cave
... that even though the Mammoth Cave system has passages directly beneath Great Onyx Cave , they have never been connected?
... that even though the <a class="mw-redirect" href="./Mammoth_Cave" id="mwB-o" rel="mw:WikiLink" title="Mammoth Cave">Mammoth Cave</a> system has passages directly beneath <b id="mwB-s"><a href="./Great_Onyx_Cave" id="mwB-w" rel="mw:WikiLink" title="Great Onyx Cave">Great Onyx Cave</a></b> <i id="mwB-0">(pictured)</i>, they have never been connected?