Agrupa Vicenta Mine Monument · La Unión, Campo de Cartagena, Murcia The Agrupa Vicenta mine is a mine from 1869 adapted for tourist visits in the Sierra Minera de Cartagena-La Unión, within the Parque Minero de La Unión, in the Región de Murcia. It is reached via the Ruta Minera del Camino del 33, an old path used by miners travelling between La Unión and Portmán. A gallery leads into a chamber of about 4,000 square metres and up to 80 metres deep beneath the slope of monte Sancti Spiritu, considered one of the largest visitable mines in Europe, with vaults up to eight metres high. Excavated using the room-and-pillar system in a pyrite-bearing vein about five metres thick known as manto de los azules, from which mainly pyrite was extracted, it also holds an underground lake with reddish waters. Photo: Nanosanchez (CC0) What to see and do in La Unión