"It's very hard to quantify what's going on in there." Researchers investigate 'black box' discovered deep in caves of the ...
Every year at Grand Canyon National Park, millions of visitors from all over the world stop at one of a dozen water spigots.
SELIGMAN, AZ (AZFamily) — Twenty-one stories deep and about a mile off of old Route 66 sits the Grand Canyon Caverns. Formed over 15 million years ago, they were discovered in 1927, and tours began in ...