In nearby Aquileia, near the course of the Natissa, high above the former Roman port which saw exotic goods of all kinds passing through, stands the mighty brick bell tower of the Basilica, slightly distant from the building, dedicated to St. Mary of the Assumption and to Saints Ermacora and Fortunato (among the first Christian martyrs).
It completes the famous monument, reconstructed in the characteristic Romanesque forms between 1021 and 31 by Patriarch Popone on the site of a previous building of early Christian worship that the inscription refers to Bishop Theodore (early fourth century).
The interior, rebuilt in Gothic style after the 1348 earthquake, preserves the extraordinary polychrome mosaic flooring of the original church, with its magniloquent and mysterious religious symbolism, as well as other mosaics, frescoes and plastic works that span almost a millennium of history, partly documented in the nearby Museum of the Patriarchate.
The present Basilica is presented, on the whole, in Romanesque-Gothic forms. The interior, majestic and solemn, is permeated with an intense spirituality, refined over the centuries. The elegant wooden ceiling with a ship's hull dates back to the fifteenth century; between the floor and the ceiling, therefore, are enclosed over a thousand years of historical and artistic events.
The floor is the largest early Christian mosaic in the western world (760 m²): it would be enough only to repay the pilgrim of the long journey to come and visit the Ecclesia Mater, World Heritage Site. The mosaic was partially ruined by the installation of the columns in the right aisle; this happened at the end of the 4th century or, according to a different opinion, after the middle of the 5th century. The foundations of the columns are in sight because at the beginning of the 20th century the medieval red and white tile floor, dating back to the time of the Patriarch Popone, was removed to highlight the precious early Christian mosaic; the crystal walkways are at the level of the medieval floor.
Below the church there are two crypts. The first, at the presbytery, is covered with Byzantine frescoes of the twelfth century (the most important cycle of frescoes of the Romanesque period in northern Italy). On the vault, nineteen scenes with the Stories of Ermacora tell the story of the origins of Christianity in Aquileia.
According to tradition, Saint Peter sent Saint Mark to evangelize Aquileia, capital of the Tenth Region of Augusta, la Venetia et Histria. In the four lunettes are depicted scenes from the Passion of Christ and the Death of Mary; in the pendentives, figures of Saints; in the central vault, the Madonna and Child enthroned among the symbols of the Evangelists and Christ enthroned among the Angels. The second, called the Crypt of the Excavations, allows a journey back in time to the time of Theodore.
Once out of the Basilica, you will find the Church of the Pagans, whose door is right in front of that of the Basilica, and the post Theodosian Baptistery connected to it. On the side, in the Süd Halle (Southern Hall of the Baptistery) you can admire the magnificent mosaic surfaces that cover the area adjacent to the Baptistery. A special protection allows the conservation and the visit of the important mosaic remains. The floor is divided into three large rectangular fields, which reproduce the space of the southern hall of the Baptistery, is decorated with motifs from the tradition of Aquileia between the end of the fourth and the beginning of the fifth century AD.
The evident traces of fire, visible on the surface of the floor, testify to a destructive event for which the area was abandoned and the mosaic surface damaged by the insertion of burials in limestone, as evidenced by the six sarcophagi on display inside the structure.