Limestone caverns featuring stalactites and stalagmites, a waterfall, and an underground lake, as well as a summer water park
It is the biggest cave found in Portugal. The cave was first entered by humans in 1947. The Moinhos Velhos Cave (Portuguese: Gruta de Moinhos Velhos) is one of the most notable cave systems in the Portuguese Estremadura Limestone Massif, stretching for around 9 kilometres.
It is distinguished by the presence of two fóssil paragenetic major conduits of approximately one decametre in diameter with dendritic tributaries, as well as a series of semi-active channels in a dendritic pattern to the north and angulate to the south. The thickness of the intermediate zone ranges from 80 metres upstream to 60 metres downstream, with a drop of 100 metres in the fossil zone. Water flows through syngenetic passages from the northern to the southern quadrants, approaching the spring at Gruta da Pena.
In the formation of a cave system, four genetic stages may be identified. The first is represented by superficial phreatic galleries of modest diameter, the second by the Galeria Gémea paragenetic main conduit, the third by the Galeria Grande and its tributaries, and the final by the lower cave levels’ active and semi-active galleries.
This cave is home to various endemic trogobionts, including the ground-beetle Trechus lunai, the cave spider Nesticus lusitanicus, and several stygobionts, the most abundant of which is the isopod Proaellus lusitanicus.
It is 15 kilometres from Fátima in the village of Mira d’Aire, which is located on the right side of the N 243 road at the entrance of Serra d’Aire, heading towards Porto de Mós.
