http://www.infoelba.com/island-of-elba/places-to-see/forts-fortresses/tower-of-san-giovanni/?_ga=1.40226402.1502365264.1464011242

The Tower of San Giovanni,built as a military defence, dates back approximately to the XII-XIII centuries when the Island of Elba was under the rule of the Pisans. The Tower, at a height of 300 metres, is on the slopes of Monte Perone overlooking the gulf of Marina di Campo - at one time one of the bays that was most at risk as regards attacks coming from the sea - and almost seems to rise up from the huge granite rock on which it stands. In those days, threats of Saracen attacks came from one side, while on the other side the hostility between Pisa and Genova who both wanted to control the Mediterranean, soon turned to war, and this explains why the Tower was in a truly strategic position both for watching over the area and for signal communication; today, tourists can enjoy the breathtaking view it offers. The Tower is square, has two floors and a control balcony, that unfortunately was completely destroyed after an enemy attack; the only openings are a window and an entrance whose only access was via a folding ladder, so as to make it more difficult for the enemies. For many, many years it lay abandoned, worsened by frequent collapses, and despite some renovation work that has at least made the walls stronger, it is very difficult to get inside. On the contrary, getting to the tower is easy: follow the winding, uphill road for Monte Perone, and at one point you will see it on your right at the end of a path: a small picnic area surrounded by fern, broom and strawberry trees.