Islands of the Mar Menor Nature · Los Alcázares, Mar Menor, Murcia The islands of the Mar Menor, together with several stretches of coastline, make up the open spaces and islands of the Mar Menor, protected sites of the Natura 2000 network shared between Cartagena, San Javier and Los Alcázares. They are five islands of volcanic origin: Mayor or del Barón, the largest, at 93.8 hectares and 104 metres high; Perdiguera, the most visited, at 25.8 hectares; del Ciervo, at 16.3 hectares, which until recently was linked to La Manga by an artificial causeway now removed; and the smaller Redonda and del Sujeto, the latter just 2.4 hectares. They were formed by the activity of ancient underwater volcanoes that shaped the Mar Menor basin, which also includes El Carmolí, the remains of another, now-extinct Quaternary volcano on the Cartagena coast. Photo: Nioger (CC BY-SA 3.0) What to see and do in Los Alcázares