It occupies an area of 383.9 km2 (148.2 sq mi) and is the most important limestone deposit in Portugal, with a variety of geological formations and climate associated with karst geomorphology and topography, such as underground caves and sinkholes.

[3] It was designated a protected area in 1979 with the intent to preserve its natural aspects, and the architectonic and cultural heritage linked to the local human populations.

[4] The park is located in the Central-West region of Portugal defining the border between the Estremadura and Ribatejo provinces, and the Leiria and Santarém districts.

It comprises part of the municipalities of Alcanena, Alcobaça, Batalha, Leiria, Ourém, Porto de Mós, Rio Maior, Santarém and Torres Novas.

The Jurassic period rocks of the limestone massif flourish to a great extent,[9] standing out by its relief as a prominent mass that rises about 200 m (660 ft) relative to its surroundings.

After infiltrating and flowing from higher ground, and on surface depressions where the rainwater outflow cannot match the inflow (such as poljes), water is naturally and ephemerally pooled, and sediment is deposited.

These phenomena justify the absence of shallow watercourses, and the presence, instead, of a vast network of underground galleries, being perhaps one of the largest freshwater reservoirs in the country, giving rise to some important water courses, such as the Alviela and Lena river springs.

:[18] Also notable are the following paleontological locations: Skeletal remains of Pleistocene brown bears have also been discovered in Algar do Vale da Pena, near the village of Moita do Poço.

[23] The park has a Mediterranean climate, with mild, rainy winters and cool to hot, dry summers but variations in temperature, precipitation and insolation occur throughout the region.

[11] The park has five main associated landscapes:[11][30] Additionally, the park has 27 different species of orchid, about 50% of all the species native to Portugal[10] and provides habitat for various calcerous flora that is uncommonly found in Portugal including: Iris subbiflora, Paeonia broteri, Paeonia officinalis, Jonopsidium abulense, Himantoglossum robertianum, Orobanche latisquama, Petrosedum sediforme, Scrophularia sambucifolia, Antirrhinum linkianum Teucrium chamaedrys, Salvia viridis, Inula montana, Aristolochia pistolochia, Teucrium fruticans, Ophrys fusca, Phlomis lychnitis, Fritillaria lusitanica and some Portuguese endemics such as Silene longicilia, Arabis sadina, Arrhenatherum pallens, Ulex jussiaei, Narcissus calcicola, Ulex airensis., Saxifraga cintrana and a newly described species in Portugal, Arenaria grandiflora, which is currently only known to exist in the park.

[31] The terrain is characteristically dry due to its porosity and so human settlements lie on and around the fertile terra rossa plains, where maize, potatoes, vines, other varied crops, and even gardens, are grown, allowing for a mosaic of colors and textures to form, with great seasonal dynamics.