Calares del Rio Mundo y de la Sima

Calares del Rio Mundo y de la Sima Natural Park protects 19,192 hectares of limestone mountain landscape in southwestern Albacete province, Castilla-La Mancha. ^[1] Designated on 5 May 2005 under Ley 3/2005 of Castilla-La Mancha, the park encompasses the spectacular source of the Río Mundo, which emerges from the vast Cueva de los Chorros in a 300-metre-high cliff face as one of Spain's most dramatic river springs. ^[1] The calares (high limestone plateaus) reach over 1,600 metres elevation and are deeply karstified, with extensive cave systems, dolines (sinkholes), and underground drainage networks. The Calar del Mundo plateau is home to the second-largest field of dolines in the Iberian Peninsula, with nearly 1,000 sinkholes recorded. ^[2] The park is located between the Sierras de Alcaraz and Segura and lies close to the neighbouring Parque Natural de las Sierras de Cazorla, Segura y las Villas (Jaén province). It is designated within the Natura 2000 network.

The forests support roe deer, red deer, wild boar, and Iberian ibex on the rocky calares. Raptors include golden eagle, Bonelli's eagle, booted eagle, griffon vulture, and peregrine falcon nesting on the cliff faces surrounding the Río Mundo source. ^[1] Otters inhabit the river system. The cave systems are important for bat conservation, with several species including greater horseshoe bat and Schreiber's bat using them for hibernation and breeding. The clean rivers support native trout populations and European crayfish. The park's avifauna includes red-billed chough on the calares, dipper and grey wagtail along the streams, and Dartford warbler in the scrubland. The Valverde's lizard, an endemic reptile of the Alcaraz, Segura, and Cazorla mountain ranges, is also present. The combination of karst terrain, dense forest, and clean water creates high biodiversity for the relatively compact area.

The calares are covered by Scots pine and maritime pine forests at higher elevations, with extensive holm oak woodland at lower levels. The Calar del Mundo summit plateau supports distinctive communities of cushion plants and mountain grasslands. Gallery forests of ash, maple, hazel, and elm line the river corridors, with particularly lush vegetation around the Río Mundo source where permanent moisture supports fern communities and mosses. Yew trees survive in sheltered limestone crevices. Wild rose, hawthorn, and blackthorn form dense scrub on forest edges. The karst terrain supports specialised limestone-crevice flora, including endemic plant species of the Alcaraz, Segura, and Cazorla mountains. Orchid diversity includes several rare species. Juniper scrub colonises exposed rock surfaces. The park contains relict populations of plants with Atlantic and Eurosiberian affinities in the humid sheltered valleys.

The calares are formed from Jurassic and Cretaceous limestones thrust over younger formations during the Alpine orogeny. Extensive karstification has created one of the most important speleological provinces in southeastern Spain. The Cueva de los Chorros cave system has been explored across more than 50 kilometres of galleries through more than 85 cavities, making it the longest cave system in the southern half of the Iberian Peninsula. ^[1] The Río Mundo source at the Cueva de los Chorros is a vauclusian spring where groundwater collected across the entire calar emerges from the cave mouth in a 300-metre cliff face. During snowmelt and heavy rain, the reventones (pressure-driven water surges) produce a spectacular cascade. The underlying stratigraphy includes Triassic red beds and gypsum that create impermeable barriers directing underground water flow. Active tufa deposition occurs below the spring.

The park's climate varies from Mediterranean at lower elevations to subhumid montane on the calares. The higher elevations receive 700–1,000 millimetres of annual precipitation, significantly more than the semi-arid lowlands of Albacete province visible from the calar edges. Snow is common on the calares from December through March. Average annual temperatures range from 12–14 degrees at lower elevations to 8–10 degrees on the highest plateaus. Summer temperatures are moderated by altitude but can reach 30 degrees in the valleys. The dramatic Río Mundo reventones are triggered by heavy rainfall or rapid snowmelt, occurring unpredictably between November and April. The climatic gradient from the dry Albacete plain to the humid mountain creates a strong ecological contrast over short distances.

The rugged terrain limited permanent settlement to the valley edges, though transhumant herders used the calares as summer pastures for centuries. Charcoal production and timber extraction provided historical economic activities. The village of Riópar developed around iron foundries established in the 18th century using local ore and charcoal, with the Real Fábrica de San Juan becoming an important industrial site. Water-powered mills along the Río Mundo processed grain and textiles. The cave entrance at the Río Mundo source has attracted visitors since at least the 19th century, with early tourism developing around the spectacle of the reventones. Mid-20th century rural depopulation affected the area, though the scenic attractions have maintained visitor interest.

Calares del Rio Mundo y de la Sima was designated a Natural Park on 5 May 2005 by the Castilla-La Mancha government under Ley 3/2005, protecting 19,192 hectares in southwestern Albacete. ^[1] Earlier protections included game reserves and the Natural Monument designation of the Río Mundo source. The park responded to threats from logging, quarrying, and unregulated tourism at the cave entrance. Natura 2000 designation provided EU-level protection. The management plan established zones protecting the cave systems and karst aquifer while permitting sustainable forestry and pastoral activities. The park cooperates with the adjacent Cazorla, Segura y las Villas Natural Park in Jaén province for landscape-level conservation of the Betic mountain system. Interpretive facilities at the Río Mundo source have improved visitor experience while reducing impacts on the cave environment.

The Nacimiento del Río Mundo (Río Mundo source) is the park's flagship attraction, where the river emerges from the Cueva de los Chorros in a 300-metre cliff as one of Spain's most spectacular natural springs. During reventones, the water volume increases dramatically, creating a cascade visible from the viewing platforms below. The Sendero del Calar del Mundo ascends to the summit plateau with panoramic views across the limestone landscape. The Cueva de los Chorros entrance can be viewed from below; cave entry requires speleological permits and specialist equipment due to the system's 50+ km extent. The Sendero del Río Mundo follows the river downstream through gallery forest. The historic iron foundry buildings at Riópar offer industrial heritage interest. Several marked routes explore the forested calares. The Sima del Horcajo is one of the deepest vertical shafts in the region, accessible only to experienced cavers.

The park visitor centre near the Río Mundo source provides information and parking for the main trail. Access is via the CM-412 from Riópar or Yeste. The nearest major city is Albacete (approximately 100 kilometres). No rail service reaches the area; private transport is necessary. Bus services to Riópar are infrequent. Accommodation options include rural guesthouses in Riópar, Cotillas, and surrounding villages. There are camping areas within the park. The trail network focuses on the Río Mundo source and the calar traverses. Entry is free. The reventones are most likely between November and April but are unpredictable, making timing visits to the spectacle a matter of luck. Spring and autumn offer the best general visiting conditions.

Protection of the karst aquifer system is the primary conservation priority, as groundwater contamination could compromise both the Río Mundo source and the cave ecosystems. Agricultural chemicals from surrounding farmland and livestock waste pose pollution risks. Logging on the calares has been regulated but not eliminated. Tourism concentration at the Río Mundo source during reventones creates congestion and erosion issues. The cave system requires strict access control to protect speleothems and bat populations. Off-road vehicle use on forest tracks damages soils and disturbs wildlife. Climate change may alter precipitation patterns critical for the karst hydrology and reventones phenomena. Conservation strategies focus on aquifer protection zones, sustainable forestry certification, visitor management at the source, and cave access regulation.