Archaeologists are hoping to discover an underwater cavern hidden beneath the imposing "El Castillo" temple, at Chichen Itza, Mexico.
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.
Water-filled caverns -- called cenotes -- sustained the Mayan civilization, and were central to its spiritual beliefs. Pictured, Holtun cenote in Chichen Itza.
The archaeologists are part of the Great Mayan Aquifer Project, which aims to learn more about the cenotes of the Yucatan and their significance to the Maya. The project is supported by the National Geographic Society.
Last month, divers from the Great Mayan Aquifer Project discovered the world's largest flooded cave, when they connected the cave system known as Sac Actun with the Dos Ojos system.
The team is led by underwater archaeologist Guillermo de Anda. He is pictured measuring a bear skull that dates from the ice age, found in a cenote.
Pictured, a Mayan altar, now underwater, discovered by the team in a cenote. These altars were used to make offerings to the Mayan rain god, Chaac.
A "Chac Mool," at the National Museum of Anthropology and History, in Mexico city. These sculptures are associated with the Mayan and Aztec rain gods.