The fort at Kélibia (Qulaybiyah), Tunisia, perches on a rocky promontory more than 150 meters high. It offers a panoramic view to the sea and to the port below (catch the view in yesterday's POTD here). A lighthouse is mounted in one of its square towers.
The site was occupied as early as the third century BC, but the fort as it stands today, is largely a 16th century (re)creation. Thick walls and towers give testimony to security contests of the past, both regular and irregular. Regular contests were waged here between the Ottomans and the Spanish, as their gun-armed galleys vied for control of the Mediterranean basin. Irregular contests in the form of piracy, privateering, coastal raids, and small-scale extortion were simply a way of life on the North African coast.
"You can see Sicily on a clear day from here," I was told by a local.
I wish I had a nickel for every "clear day" experience I haven't had.