Hidden tunnel could lead to Mayan 'entrance to the underworld'

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Archaeologists are hoping to discover an underwater cavern hidden beneath the imposing "El Castillo" temple, at Chichen Itza, Mexico.
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Chichen itza, in Yucatan state, is one of the most impressive achievements of the ancient Mayan people. Pictured, thousands of tourists surround "El Castillo" during a spring equinox celebration.
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Water-filled caverns -- called cenotes -- sustained the Mayan civilization, and were central to its spiritual beliefs. Pictured, Holtun cenote in Chichen Itza.
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