According to a report by CNN, archaeologists in Mexico will begin to excavate a secret tunnel thought to lead beneath a pyramid built by the ancient Maya. Sealed off centuries ago by the Maya, archaeologists plan to excavate it in order to reach a hidden "cenote," or underwater cavern, that had been central to Mayan spirituality. Cenotes are water-filled sinkholes and are the only source of fresh water in Mexico's Yucatan state.