Hidden beneath Mexico’s Yucatan Peninsula lies a breathtaking marvel of nature.
The Sistema Sac Actun is the world’s longest underground river system, stretching an incredible 95 miles.
This epic network of submerged caves and winding tunnels, discovered to be connected in 2018, spans more than 150 kilometers through limestone caverns, carrying crystal-clear water through one of the most ecologically and culturally rich regions of the world.
Sistema Sac Actun, meaning “White Cave System” in Mayan, is located near the popular tourist city of Tulum.
The intricate cave network was formed over millions of years as rainwater slowly eroded the peninsula’s porous limestone, creating tunnels, caves, and sinkholes, or cenotes, which have long been sources of fresh water and spiritual sites for the Maya people.
Today, it is a natural wonder, boasting countless stalactites and stalagmites, underwater chambers, and extraordinary biodiversity.
The discovery of the interconnectedness of Sac Actun with another nearby cave system, Dos Ojos, confirmed it as the longest underwater cave system in the world.
Divers from the Gran Acuífero Maya (GAM) project made the connection in early 2018 after years of exploration, solidifying Sistema Sac Actun’s status as a world record-holder.
This expansive river system is more than just a geological marvel.
The Yucatan’s underwater caves and rivers have revealed invaluable archaeological finds, including ancient human remains and animal fossils dating back more than 10,000 years, offering critical insights into prehistoric life and early human migration.
The caves are also filled with Maya artifacts, which highlight the profound cultural significance these cenotes held for ancient Maya civilizations.
The Maya believed cenotes were portals to the underworld, and many such sites in Sistema Sac Actun served as ritual spaces for offerings and ceremonies.
Sistema Sac Actun’s ecosystem is a delicate one, inhabited by unique and vulnerable species such as blind cavefish, freshwater shrimp, and specialized algae.
GAM and local environmental groups have advocated for responsible exploration and sustainable tourism practices to protect the caves from potential damage due to pollution or overuse.
For visitors who wish to experience Sistema Sac Actun, local guides offer cave-diving expeditions, snorkeling tours, and educational excursions to a few accessible parts of the system.