A fortress in the sky

Starting life in the 10th century as a lone watchtower high in Italy's Apennine Mountains, the fortress called Rocca Calascio gained more heft over the next few hundred years. Four more towers and heavy walls were gradually added around the original structure. These fortifications made clear that Rocco Calascio was ready for any military rivals who might scale the slopes from the valley below to attack this garrison.
© Francesco Russo/eStock Photo