pre-Hispanic settlements

A scuba diver measures the length of Sac Aktun underwater cave system as part of the Gran Acuifero Maya Project near Tulum, in Quintana Roo state, Mexico January 24, 2014. Picture taken January 24, 2014. Credit: Handout via Reuters/ Herbert Mayrl/Courtesy Gran Acuifero Maya Project (GAM)

Explorers Discover World’s Biggest Flooded Cave in Mexico