The forum in Zadar has been built by the first Roman emperor Gaius Julius Caesar Octavian of what the inscriptions in stone dating back to the 3rd century give evidence when the construction came to an end. It was once closed by a portico with galleries on the first floor, and under the portico there were shops.
Since the first century B.C. the forum has been the main gathering place for Roman soldiers, religious people, bureaucrats of the Republic and later of the Empire, as also for traders and all Zadar citizens in ancient times. In the time of its full glory, the forum was surrounded from three sides by a magnificent portico. It is indispensable for a walk and also one of the symbols of the city.
https://zadar.travel/attractions/attractions/forum