Gonio's fortress, an impressive piece of Roman-Byzantine military architecture, covers 47,000 sq metres within a rectangle of high stone walls with 18 towers. Built by the Romans in the 1st century AD, it was occupied by the Byzantines in the 6th century and by the Ottomans in the 16th century. An interesting little museum sits in the middle of the site with a cross outside marking what’s believed to be the grave of the Apostle Matthias.