As laid down in the practical guidelines for the implementation of the World Heritage Convention, the sites that are included in the World Heritage list must have an outstanding universal value that distinguish them from any other property and that reflects the criterion on the basis of which the World Heritage Committee decides to include it. In the case of the Tower of Hercules, its outstanding universal value lies in that it is:
- The only Roman lighthouse in the world that survives, if not complete, more than 60% of it and continues to be used today.
- It is, furthermore, a paradigmatic case of an architectonic intervention in a monument of the Antiquity because when in 1790 Eustaquio Giannini designed the restoration project of the Tower of Hercules he did so on the basis of scientific criteria, showing an absolute respect for the integrity of the lighthouse and preserving its authenticity. For this reason, this refurbishment, far from being negative, is yet another value asset as it demonstrates the sensitivity of men and women of the 18th century when restoring the received heritage.
It is for all the above reasons that the Tower of Hercules provides humanity with insight into the aid to navigation techniques since Roman times up to now. It is in this sense an exceptional reference through which to study the development and the evolution of the different signalling systems and aids to navigation since the dawn of our time up to the present.