Roman Forum of Zadar is the largest on the eastern side of the Adriatic sea, founded by the first Roman Emperor Augustus, as shown by two stone inscriptions about its completion dating from the 3rd century.
Ancient Zadar (or Iadera as the Romans would say) was a Roman colony from 48BC until the disintegration of the Roman empire in the 5th century. After a violent earthquake in the 6th century, the buildings surrounding the forum were destroyed. The still standing elements and stones (then used to rebuild) were retrieved for various buildings.
Most striking is the decorative column marking the western side of the forum. Notice the chains still visible on the column. During the Middle Ages it was the 'pillar of shame' used to punish evildoers.
Continuing on the western side of the Forum, you come to the remains of the Capitolium which was an important temple consecrated to Jupiter, Juno and Minerva.
To round out an appreciation of Roman Zadar, take a look at Zadar's Archaeological Museum which displays artifacts from the Roman period as well as a scale model of the original Roman forum.
References:Duino Castle was built by the Wallsee family in 1389 on the cliffs overlooking the Gulf of Trieste. It replaced an older castle from the 11th century. Over time, the Wallsee family disappeared and the castle, after having been used as a prison, became the residence of the Luogar and Hofer.
At the end of the 19th century it became the property of Prince Alexander von Thurn und Taxis from the Czech branch of the House of Thurn and Taxis. It remains with the family to this day with his great-grandson Prince Carlo Alessandro della Torre e Tasso, Duke of Castel Duino the current owner. The castle has been opened to the public as a museum and park.