Redwall Limestone Cavern is one of the largest of the caverns in the Grand Canyon. The cavern is approximately 300 feet wide and 150 feet from front to back. Its vaulted ceiling is about 100 feet high at its apex. John Wesley Powell estimated that it would seat as many as 50,000 people theatre style.
De Mente, Boye. Grand Canyon Answer Book. [Phoenix, Ariz., USA]: Phoenix Books. [c1989]. Page 43.
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