Following the collapse of the Roman Empire, the intensity of maritime traffic was considerably reduced and the Tower began to lose the leading role it had had as aid to navigation to become a mere watchtower or a vantage point from which the Gulf of Artabro was dominated. The great fleets that in days gone by had sailed the coasts of Gallaecia on their way to Britannia disappeared and with them the light of the lighthouse burned away, plunging the profiles of the cliffs of the north-western into darkness.

It was a time of oblivion and abandonment, during which the lighthouse gradually and seriously deteriorated and the outer ramp around the central core for access to the beacon as well as the four outside facades that protected it collapsed. The gales, saltpeter and rain that batter this area during winter storms must have gradually undermined wall mortars, but also human intervention proved determinant as during this time the Tower became the quarry for the city and its ashlars were taken away one by one by the locals to be reused in the construction of the new buildings that were then being made in the city.

The destruction of the ascending helicoidal ramp around the outside of the Tower of Hercules, of which there were hardly remains by the 14th century, meant the disappearance of the only access to the upper section of the building and the different chambers inside.

When the Tower recovered its function as aid to navigation, it was necessary to design a system to gain access to the top section to fuel the lighthouse. The solution taken was the construction of an inner staircase that connected the base of the Tower with the lantern, although this meant cutting through some of the domes from Roman times.

Further information on Staircase [.PDF]