It is common for old coastal towns to have a fortress that protected the settlement from attacks from the sea. So why is there no such fortress in Nerja? Well, there was one, called Castillo Bajo (the Lower Castle).
It was built in the 10th century by the Moors, during their occupation of the Iberian Peninsula, and served as a military fortress and residential palace for many years. The castle was strategically located on a hill overlooking the town and the Mediterranean Sea, where the current Balcony of Europe is situated.
Castillo Bajo was considered to be an important stronghold for the Moors. In 1487, the castle was besieged and captured by the forces of the Catholic Monarchs, Isabella I of Castile and Ferdinand II of Aragon, as part of their campaign to reconquer Spain from the Moors.
So where has the fortress gone? Like the rest of the area, between 1810 and 1812, Nerja had been occupied by French troops, and was valued enough by them to be told in 1810 to build its own town hall to look after its municipal affairs, separate from the region’s capital, Vélez-Málaga. It is believed that around October 4th, 1811, the British had landed in Nerja and blown up Castillo Bajo in order to keep Napoleonic forces away from it. The British also handed out 6000 rifles to the local militia. According to local records the wood from the destroyed castle was collected and sold, with the money going to buy food for the local freedom fighters (guerrillas). Over time, the remaining structures deteriorated and were further damaged by erosion and earthquakes.
There are speculations that the ruins of Castillo Bajo can still be found on the sea bottom. However, there is no concrete evidence to support this theory, and no underwater ruins have been discovered to date.