La Sima de las Palomas se ubica en la ladera sur del Cabezo Gordo, en la pedanía de Dolores de Pacheco del municipio de Torre-Pacheco, en la Región de Murcia, sureste de España. La entrada está a unos 80 m sobre el nivel del mar y permite una vista panorámica del Mar Menor, que es una laguna mediterránea de agua salada.
El Cabezo Gordo es un cerro aislado de mármol del Permo-Triásico que se alza en el sector norte de la amplia llanura del Campo de Cartagena, con una altura máxima de 312 m s.n.m. y una longitud de poco más de 3 Km.
Bajo un punto de vista geológico-regional este cerro pertenece, dentro de las Cordilleras Béticas, a la Zona Bética y más concretamente al Complejo Tectónico del Nevado-Filábride. Estratigráficamente está constituido por unos 100 m de mármoles tremolínicos (magnésicos) del Trias y bajo ellos aparecen unos micaesquistos grafitosos con vetas de cuarzo y cuarcitas del Permo-Trias.
SIMA DE LAS PALOMAS DEL CABEZO GORDO is a natural karst shaft on the south-facing hillside of Cabezo Gordo, overlooking the village of Dolores Pacheco 10 km from the town of Torre Pacheco in the Murcian Region of SE Spain. From its mouth of the gaping hole at 80 m above sea level a sweeping view takes in the vast Mar Menor (Lesser Sea) which is a salt-water lagoon of the Mediterranean Sea (Greater Sea).
Cabezo Gordo is 3-km long hill of Permo-Triassic marble that rises up majestically to a height of 312 m above sea level, in splendid isolation, in the northern part of the Murcian coastal plain (the so-called Campo de Cartagena).
A large marble quarry on the northeastern end of the hill continues a tradition of marble quarrying here that goes back to Roman times when marble was taken to the important sea-port of Cartagena. The name Cartagena is derived from the Latin Cartago Nova, or New Carthage, so called because it had been founded by the Carthaginians before being seized by the Romans two centuries before our era. In the nineteenth-century iron-ore (magnetite) mining exploited veins within the marble of the metal which outcrop on the southern flank of the hill. Both open-cast quarrying and tunnelling were practised, and the miners tunnelled into SIMA DE LAS PALOMAS around 1900 (before the iron ores on the hill finally had become worked out by the time the 1914-18 World War began).
Geologists place Cabezo Gordo in the Nevado-Filábride tectonic complex of the mountainous Betic Zone of southern Spain. 100 m of Triassic magnesian tremolinic marble follow Permo-Triassic graphitic micaschists containing quartz and quartzite veins. Less clear is how this Mesozoic mass has survived as a solitary hill rising above a plain where Quaternary sediments predominate, remnants of which are nevertheless conspicuous by their absence from the slopes and hillside.