Mazarrón is a municipality in the autonomous community and province of Murcia, southeastern Spain. The municipality has an area of 318.7 square kilometres (123.1 sq mi), and a population (2008) of more than 34,351 inhabitants.
A military fort (named C1 or Castillitos-small castles) built between 1930 and 1936 during the reign of Alfonso XIII of Spain and the Second Spanish Republic exists as a tourist attraction on the old road between Mazarrón and Cartagena, and although it is accessible from the Bay of Mazarrón it is not in the municipality itself. Some of the things that must be seen: The Bay of Mazarrón is sheltered by the last foothills of the Sierra de la Almenara, a mining area since the Carthaginian era. Over 35 km of beaches, unspoiled coves and rocky sea beds make this the ideal place for relaxing in the sun, enjoying nautical sports and scuba-diving. Due to the nature of the surrounding rocks, (see mining area and Betics mountain range),however, the beach at Bolnuevo is of coarse grit, as are most of the beaches along this part of the coast.
The Torre de los Caballos on Los Caballos peak are just a stone's throw away, built for the towns protection against pirates from the mid-16th to the early 18th centuries. The Bolnuevo Erosions, sandstone monuments sculpted by the water and wind, are another sight well worth seeing. Based right near the shore in Bolnuevo these are well worth the trip with many restaurants and a beautiful beach near by. The economic development of the early 20th century led to the construction of emblematic buildings in the style known as Murcian Modernism, including the Mazarrón Town Hall and the former Cultural Athenaeum. The great guns in Cartagena are an amazing sight. Built to defend the vital port of Cartagena in the 20th century, these guns alongside the fort and other coastal defences are a marvel into the defenses Spain went through during the early 1900s. Standing 56 feet long, weighing a total of 88 tons each and being able to fire at a range of some 20 miles. Note: the road to this area, which passes through Campillo de Adentro, needs to be taken carefully, and the "improved" car parking facilities are in extremely poor condition. For the more adventurous there is the monument of Jesus in Mazarron. This emblematic figure of Christ is perched right on the top of the Cabezo del faro, the highest point of the rocky cliffs which envelop Mazarron, close to the lighthouse. With great views and a nice walk this can be a day to remember.