It is believed that as much as another mile could be added to the survey by just mapping the known passages which have yet been surveyed.

There is no known passage between the two structures.

Famous for the 1869 three-month river trip down the Green and Colorado rivers that included the first known passage through the Grand Canyon.

The Clearwater cave, with approximately 60 kilometers of known passages, is considered the longest cave system in Southeast Asia.

The cave consists of approximately 3 miles of known passage and an unknown amount of unexplored passages.

This discovery went unused for some time, as ships continued to use the known passage through the Strait of Magellan.

The cave system includes the largest known underground passages and cave chamber discovered in the Western Hemisphere.

While surveying Lower Cradle Hole Cave, one caver sent a floating candle downstream along the river, until it floated under a low ceiling out of sight at the end of the known passage.

This observation may account for the diversity of the expression in that known passage of the prophet Micah, TO DO JUSTLY, AND TO LOVE MERCY.

He is famous for the 1869 Powell Geographic Expedition, a three-month river trip down the Green and Colorado rivers that included the first known passage through the Grand Canyon.