Sistema Sac Actun

Sistema Sac Actun is an immense flooded cave and subterranean river network on the Caribbean side of Mexico’s Yucatán Peninsula, extending north and west of Tulum. Its explored reach grew as separate systems were connected, including Nohoch Nah Chich in 2007, Aktun Hu in 2011, and Dos Ojos in 2018, making it at times the world’s longest surveyed underwater cave system. As of January 2023, it had 259.5 kilometers of explored underwater passages, or 386.122 kilometers including connected dry caves. The system is also important for preserved remains, including a mastodon and the teenage girl known as Naia, linked to early human habitation in the Americas.

Quintana Roo · Mexico