Set in limestone cliffs hidden in the jungle, they were discovered in 1878 by a group of explorers, including the American naturalist William Hornaday.
William Hornaday was a well known explorer.
mnli hypothesis: William Hornaday was a well known explorer. premise: Set in limestone cliffs hidden in the jungle, they were discovered in 1878 by a group of explorers, including the American naturalist William Hornaday.