The 170-meter Apokalypse within Blauhöhle

Beneath 21 metres of liquid, the Blauhöhle begins its westward journey. This horizontal labyrinth spans 1,200 metres or 3,900 ft. The maximum depth of the cave under water is 42 metres (138 ft) before it comes above the level of ground water and opens into a second big air-filled chamber. Ancient currents from the Danube presumably shaped this void. Now, the Schmiech, Ach, and Blau carve through the Swabian Alps in Germany. This remains the region's largest cave system.

In 1985, Jochen Hasenmayer found a sanctuary above the water line. He dubbed this space Mörikedom or Mörike Cathedral. Divers navigate the drowned maze to reach such dry heights. Though exploration paused after a Wolfgangsee accident, the Arbeitsgemeinschaft Blautopf resumed the quest. New breathing technology allowed explorers to reach the Wolkenschloss, a large air-filled cavern discovered by the Arbeitsgemeinschaft Blautopf.

Past the Mörikedom lies the Landweg, an open subterranean river. In autumn 2006, this route unveiled the Apokalypse. This staggering room measures 170 m or 560 ft long by 50 m or 160 ft wide and high. Two teams now pursue the horizon. Since 2002, the Arbeitsgemeinschaft Höhle und Karst Grabenstetten sought a dry door after linking the Vetterhöhle to the Wolkenschloss. Meanwhile, others study a Blaubeuren sinkhole to find paths beyond the Apokalypse.

Sources: Wikipedia, OpenStreetMap, Wikidata, Wikimedia Commons