Its almost 5,000km², of which a good half is designated as a core zone, constitute a stronghold against the further tourist development of the Yucatec Caribbean coast to the south.

Sian Ka’an lies on a partially emerged coastal limestone plain that is part of the extensive barrier reef system along the Central American coast. A large part of the reserve belongs to an area that dates back to the late Pleistocene and is crossed by a belt of karst holes (cenotes) which are characteristic for the Yucatán Peninsula. The groundwater level is close to the surface, but there is almost no running surface water because it quickly seeps through the thin layer of brown earth into underground channels. Thus the soils of the reserve are unsuitable for cultivation.

Sian Ka’an has been a Unesco World Heritage Site since 1986. It owes this status to its unique flora and fauna and 23 archaeological sites. In the extensive wetlands, 103 mammal species have been registered, including howler monkeys, foxes, ocelots, pumas, raccoons, caimans and occasionally jaguars. There were 336 bird species counted, among them frigate birds, vultures and eagles. Four of the six species of sea turtles use the beaches of Sian Ka’an to lay their eggs between June and August: green sea turtles, hawksbill turtles, loggerhead turtles and leatherback turtles.

A human settlement could be proven since the pre-classical period of the Maya culture (approx. 200 A.D.). Known leaders from this period were Cohuah and Uaymil. Today the area has over 2000 inhabitants. Boat tours with a special natural history guide or kayak tours on your own are offered on site. Due to the proximity to Tulúm this is an ideal day or half day tour.