Its origins date back to 1194, when Alfonso II of Aragon, and his wife Doña Sancha donated an old Moorish castle to the monks of Poblet to build a monastery and to establish the Christian faith in the area.

Followers of Islam sought to establish their cities on the rivers banks because their economy was based on agriculture, which was performed through laboring irrigated lands.

This is why they chose to live on low lands and did not effectively occupy the higher areas of the Pyrenees, where they merely controlled the traffic of people and goods through fortified steps at the entrance of the valleys.

During the reign of Pedro IV the differences between monks and residents in 1335 caused the king to receive the Stone Monastery with their vassals under his tutelage.

One had to cross the medieval keep to gain entrance through the walls The church opened into the cloister, noted for its great arches, and the various premises of the monastery.

In February 1836, the Mendizabal Confiscation Ecclesiastical Act declared the sale of all property belonging to the regular clergy, and the proceeds were intended to amortize the debt.

The decree was part of a program that sought to win the Carlist Civil War to raise funds and troops to restore confidence in the credit of the State and in the long term, allow for tax reform.

Since it was abandoned in 1840, Pablo Muntadas Campeny, a Catalan wealthy merchant, bought the monastery, maintaining farming and livestock in the place.

He explored the existing caves, cleaned and opened a path, and brought beautiful tree species, bearing a spa to the condition and use of medicinal waters spas of the era.

The canyon itself includes a network of mossy, garden-like caves (natural and man-made), waterfalls and lagoons that contrast with the otherwise dry hills of southern Aragon.

In 1959, a dam was constructed across the river, which created the 1300 acre La Tranquera Reservoir, flooding part of the canyon, some of the best local farmland, and several villages.

At lower elevations, there are also cultivated Aleppo pine (Pinus halepensis), walnut, horse chestnut, ash, maple, laurel, and cypress trees.

Near the water there is a diverse flora, including willows, belfry, reeds (Phragmites australis, Typha angustifoli, Juncus articulatus, Juncus inflexus), grasses (Imperata cylindrica), yellow iris, poplar, tamarisk, plum feral, cherry feral, elms, vines (Clematis vitalba, Vitis vinifera, and ivy), wild roses, wild broom (Osyris alba), dewberries and blackberries.

Many mammals live in the park, including foxes, beech marten, wild boars, rabbits, deer, badgers and genets, though not in large numbers.

Several European thrush species and the barbary dove are numerous enough to influence the dispersal of plants like Celtis australis, Cynanchum acutum, and bittersweet nightshade.

The Tranquera Reservoir and Gallocanta Lagoon create marsh land, which are home to mallards, ducks, pochard, coots, teal, herons and cormorants.