Although we did not actually get into this biggest section, we were in part of the cave system in October-November 2011 and again in 2012 with our SE Asia Karst Tour. In 2012 we also had an evening with Howard Limbert and listened to him talk about the history or 20 years of cave exploration in this part of Vietnam.
News story with great photos: http://tinyurl.com/kar5qwq Son Doong Cave's website: http://tinyurl.com/9mdrl67 Dwight
