"Far below them they saw the white waters pour into a foaming bowl, and then swirl darkly about a deep oval basin in the rocks, until they found their way out again through a narrow gate, and flowed away, fuming and chattering, into calmer and more level reaches." --The Two Towers The Forbidden Pool was a basin of water created by the waterfall that concealed one of the two entrances into the hiding place of the rangers of Ithilien.