The site called “Arco del Tiempo del Río La Venta” (Arch of Time of La Venta River), is located on an area of geological formations over 87 thousand years old, with predominant karst landforms, because of limestone dissolution. Part of La Venta River is skirted by high cliffs, forming a canyon with limestone walls that reach heights over 500 meters. This canyon has a length of 84 km and many natural caves have been formed in its walls. The whole ensemble is a karst system, which added to tectonic factors, has originated depressions that can be physically observed such as abysses, fissures, dolines and caverns.

It stands out the López Mateos karst system (named as such given its proximity to the homonymous community) which brings together speleological, natural and archaeological wealth in a tropical karst area, unique and emblematic (Bernabei et al. 1999). The caves of La Venta River keep much archaeological evidence of its Prehispanic occupation, as well as important characteristics from the point of view of stratigraphy and culture. The climatic features and the geological context of the area have allowed that artifacts made with organic materials that are rarely conserved in open archaeological sites have been conserved in several caves of the Canyon of La Venta River.

The area has a warm subhumid climate where the shallow hydrology is virtually absent; however, El Ocote Rainforest has an important subterranean river complex, laying an interesting dynamics of underground water circulation in permanent linking with the karst system. The average annual temperature ranges from 21 to 28°C, with an average of 25°C. Rainwater is captured by the extensive rainforest and is driven to the bottom of the dolines, forming a wide hydro-geological collector, capable of storing almost 20 cubic meters of water per second (Giulivo, 1999).

The complex and varied cave system of karst origin that exists in the area is a perfect habitat for many animals that develop their lifecycles inside them or that use them as places for refuge. From the point of view of ecology, the caves are characterized by a very high relative humidity, constant temperature and absolute darkness. Its fauna is composed by organisms with different levels of adaptation to the selective conditions generated by the dark and humid atmosphere of the caves (Sbordoni, 1999). The most evident adaptations of the cavern fauna are morphological and become apparent by the loss of pigmentation in their bodies, the extreme reduction of the eyes to the true anophthalmia and the lengthening of all the appendixes.

In La Venta River Canyon is located the highest natural arch on the planet, 158 meters high, 255 m. long and 35 meters wide. This geomorphologic formation of over 80 million years joins other several scenic beauties of the landscape such as the cascades of La Conchuda and El Aguacero. There are also more than 400 caves with planimetric tours of up to 13 km. Such is the case of the cave of La Venta River, considered as the second largest of the State of Chiapas.

Likewise, more than 38 abysses can be appreciated in the site, with diameters over 100 m. and depths from 100 to 280 m., like Las Luchas abyss, which is the deepest in the area and the third in the country.