What you will see
Cave galleries, Hard restrictions, Restrictions, Rock Formations
The spring of the Almonda river (or "Olho do Moinho da Fonte") is located on the southeastern ridge of the Serra de Aire, Torres Novas anticline resulting from, among others, contact between the Estremenho Calcário Massif and the less permeable soils of the basin of the Tagus.
This karst spring is the exsurgence of the underground hydrological network of the most extensive national karstic system. The Almonda grotto has an approximate development of 10km, with an extensive network of underground, fossil or active galleries. Due to its complexity and size, its exploration and documentation is yet to be completed.
Although the spring is permanent, it is only possible to dive on dry season. It is possible to go trough 1000mts of galleries and a drop of -78mts. In the rainy season, it is impossible to penetrate the system at the source due to the strong current and flow rate. Authorization from the Renova factory is required. (Luís, R. 2018)
-- Spot description by Rui Luis