[2][3] The limestone formation containing the system is approximately 100 metres (330 ft) thick and sits on a massive water-resistant layer of marl.

[7] The karst complex of Ojo Guareña consists of a massive network of over galleries and cavities, not all of which are connected, occupying an area of about 13,000 ha.

The groundwater runs through Ojo Guareña at a speed of 1.5–5 km per day, depending on whether the measurement is made during the drier summer or the flood season.

[6] The vegetation in the Ojo Guareña area is very diverse due to its location in a transition zone between the Mediterranean and Euro-siberian climate regions.

A number of types of trees are found in these forested areas, including multiple varieties of oak, beech, hazel, poplar, alder, pine, and aspen.

[10] Impressions of footprints making a round trip, accompanied by torch fragments that have been radiocarbon dated to as old as 15,600 years, indicate that the cave has been in use for millennia.

[12] On the walls and the vault of the Sala de la Fuente, or Fountain Room, are paintings that depict people, animal forms, and geometric drawings.