Portogruaro was founded in the XII century on the remains of an ancient Roman town. The Germanic influence can be seen in the urban layout and, in fact, Emperor Ottone donated the land along the River Lemene to the Bishop of Concordia, which the current Portogruaro grew from. Further demonstration of their bond is the Germanic origins of the majority of the bishops of Concordia and patriarchs of Aquileia during that time. Portogruaro founded its wealth on trade, like many German towns.
Evidence of ancient Portogruaro still remains, such as the historic town centre and Town Hall which dates back to 1265 built with fair faced bricks, the Mill, two symmetrical buildings built on the bed of the River Lemene, the gates of Saints Agnes, John and Gottardo, the only three left of the original five which gave access to the town when the fortified walls still stood. Nearby Concordia Sagittaria was also founded in Roman times in 42 A.D. between Via Postumia and Via Annia. After the barbarian invasions it became part of the Cividale Lombard Duchy. In the Middle Ages it was part of the Friuli March and later of the Aquileia Patriarch. In 1420 it was incorporated into the lands of the Republic of Venice.
In 1838 Concordia was separated from the Friuli lands to be incorporated into the province of Venice. The Cathedral of Saint Stephen Protomartyr is well worth visiting. Dating back to 1466 it was terminated in the XIX century when the choir was built. Beneath the Cathedral of St Stephen the remains can be seen of the primitive Basilica Apostolorum Major, built to house the relics of the Saints John Baptist, John Evangelist, Andrew, Luke and Thomas. Inside there is a holy water stoup from the I century B.C., a number of frescoes and a beautiful baroque altar.
To the right of the temple stands the XII century bell tower. The City Hall is near to the cathedral, and in the square in front of the church archaeological digs began recently which have unearthed a section of a roman road, with clear signs of the furrows left by the carriage wheels. In a side street of Via Claudia a stretch of the town walls and the baths can still be seen, dating back to the II – III century A.D. The Baptistery, built by Bishop Reginpoto in 1168, stands behind the Cathedral.