If you have a car, then a short trip down the coast will get you an interesting close-up view of a number of the old watchtowers. Plenty of watering holes along the way, so make it a leisurely day out.
In the relatively short distance between Torre del Mar and Nerja there are no fewer than five of the ancient defensive watchtowers. These towers were generally built in the 15th century, some a little later, and were designed to keep an eye out for unwelcome visitors from Morocco and elsewhere. The towers tend to be around 12 metres tall.
They all have, to varying degrees, been renovated or rebuilt.