Santuario della Beata Vergine Marcelliana

Monfalcone Cathedral was built between 1926 and 1929 on top of an old 18th-century church, traces of which can be seen behind the present cathedral. This church was itself the restoration or reconstruction of an ancient church of medieval origin. During the hostilities of the First World War, the bell tower collapsed on the building, eventually destroying the church. At the end of the war, the only remaining place of worship had to be rebuilt, hence the construction of the present neo-Romanesque building in the 1920s.

The Patriarchal Basilica of Aquileia was the spiritual centre of the ancient Patriarchate of Aquileia and played a key role in the evangelisation of much of Central Europe in the early Middle Ages. Its oldest remains date back to the 15th century, the present basilica was built in the 11th century and renovated in the 13th century. The Patriarchal Basilica of Aquileia and the archaeological area are included in the World Heritage List established by UNESCO in 1998.

The Metropolitan Cathedral of the Martyrs Saints Hilary and Tatian dates from the 13th century. In 1471, the Chapel of St. Acacius, the best preserved part of the cathedral, was built. Between 1682 and 1702, the church underwent a radical Baroque renovation: Giulio Quaglio painted a series of frescoes that were lost during the First World War. In 1751, Gorizia became the seat of the archbishopric following the dismantling of the patriarchate. It was severely damaged during the First World War: it was returned to worship in 1928, as recalled by a plaque outside, in its present form.