In ancient times, there used to be a wide stretch of navigable sea opposite the springs of the Timavo, known as the Lacus Timavi, roughly covering the area of Lisert today. The term Lisert itself derives from the Latin word desertum, used by the Romans to indicate areas close to their borders, or limes. During the Middle Ages, the name evolved into ‘Lisertum’, then into ‘Desert’ and finally into ‘Lisert’. The lacus was a large lagoon area protected by two small limestone islands called Insulae clarae, later named Punta or Amarina and S. Antonio. It was thus a natural port with jetties at San Giovanni di Duino, which the Romans further endowed with thermal baths and recreational areas subsequently much used by the people of Monfalcone and, later, by the Venetians.