'Ana 'Ahu, often referred to as the "Smoking Cave," is a haunting sinkhole that descends deep into the abyss, its true depth remaining a mystery. Located amidst the enchanting 'Eua forest, a short but steep (and occasionally slippery) descent via concrete steps leads you to a wooden platform overlooking this enigmatic natural wonder. The name "Smoking Cave" arises from the gentle waterfall that produces a misty ambience around it. If you're unable to reach this site independently by foot or 4WD, it's a frequently visited destination on 'Eua island tours.