Under Lombard King Cunipert, the Synod of Pavia takes place where the representatives of the schismatic clergy of the ecclesiastical province of Aquileia officially accept the decrees of the 5th Ecumenical Council (Constantinople II) and finally desist from their schism; narrative account from the contemporary "Poem on the Synod of Pavia" (Carmen or Rythmus de Synodo Ticinensi).
Emperor Lothair I confirms the immunities enjoyed by the Church of Aquileia and its right to canonically elect their patriarchs.
The first pact between the Western Roman Empire, represented by Emperor Lothair I, and the Duchy of Venice, represented by Doge Pietro Tradonico, sanctioning mutual aid in campaigns against the Slavs and defining the rights over the use of land as well as the modalities of justice administration. This is the first "international" treaty in which Venice partook as an autonomous polity, independent of the Byzantine Empire.
Emperor Louis II assumes under his protection the monastery of St. Michael in Diliano and its abbot Felmo, bestowing upon the monastery immunities and the right of free election of its abbots.
Emperor Louis II confirms the charter of Lothair I to the Patriarchate of Aquileia regarding the dispute with the Patriarchate of Grado that was settled at the Synod of Mantua in 827: the patriarchs of Aquileia are to enjoy the metropolitan jurisdiction over all the Istrian bishoprics.
King Berengar I donates two forts, the Vermes (Beram in Istria ?), to the Bishopric of Trieste (10th- or 11th-century forgery).
King Hugo donates Sipar, Umag, and Monfalcone to Radald, the bishop of Trieste, and places the Bishopric of Trieste under his royal protection; a forged charter.
King Henry IV donates to Patriarch Sigehard and the Church of Aquileia the County of Friuli, the village Lucinico, and all the rights and properties that Count Ludwig had in the said county.
Henry IV, King of the Romans, explains the reasoning behind the donation of imperial rights over the Bishopric of Trieste to the Patriarchate of Aquileia and confirms the said donation.