The first building of the church - founded in 639 on the request of the exarch of Ravenna Isacio and with the help of the magister militum Maurizio - was dedicated to the Mother of God and is the oldest in Venice; this is explained in an inscription discovered in 1895, still visible today next to the main altar.
Two great restorations later followed one another: the first towards the middle of the 9th century under Bishop Adeodato II, who laid the mosaic floor with black and white tesserae with floral motifs, the second - by order of Orso Orseolo Bishop of Torcello - in the early years of the 11th century; when the church was named Maria Assunta. The cathedral took on the appearance that we can still admire today during the second restoration.
It was an episcopal seat until the end of the 17th century, a historical period in which Torcello experienced its heyday which - as well as being the seat of hard-working metal, glass and wool factories - was one of the most important ports of Venice thanks to the three channels that run to it: it was precisely for this reason that it was also defined as a large marketplace by the Byzantine emperor Constantine Porphyrogenitus.
To access the Cathedral one passes through a very tall portico that precedes the entrance itself. Once through the threshold, one immediately realises that the plan is divided into a nave and two aisles, each ending in an apse. As shown by the Early Christian architectural plan, the Baptistery stood in front of the cathedral’s façade, whose remains are still visible today and maintain its original circular structure, dating back to the 7th century.
The principle motif of the cathedral is the Marian figure, and the image was depicted in the center of the building overlooking the faithful surrounded by a golden sky, created by means of the apse semi-dome, under which the Apostles are represented. Inside are many mosaics of truly imposing size, shining with a very unique light and designed to create a theological path from darkness to light. The first represents the Universal Judgment (placed to the west, on the wall above the portal of entrance) connected through the colonnade of the central nave (composed of nine columns of Greek marble and surmounted by beautiful Venetian-Byzantine capitals) to the shining apse semi-dome of gold, symbol of eternal life.
During this metaphysical journey you can walk on wonderful floors full of geometric patterns and will be filled with a sense of solemnity due to the precious marbles that adorn the place and the original wooden ceiling. Thanks to some imposing restoration work, the high altar was rebuilt with its original material in 1929 and a sarcophagus of Roman origin with the remains of Saint Heliodorus was placed in the lower section.
The tombstone of the Bishop of Torcello Nicola Morosini (who died in 1305) is still preserved and can still be seen on the left side chapel while one can admire Christ Pantocrator among the archangels Gabriel and Michael in the central apse, framed by the images of the Saints: Augustine, Ambrose, Martin and Gregory in the lower section. On the right we can also observe a 12th century mosaic with very precise and delicate workmanship depicting Four Angels. Resting above the two altars of the side aisles are two wooden panels depicting the sanctified figures executed by the 15th century engraver Paolo Campsa.
One can see fragments — still well preserved — of balustrades, screens and friezes in the sacristy, including the well-known Pluteus (Panel) with the wheel and a statuette, dated to the 15th century and attributed to the Florentine artist Pietro Lamberti, depicting the Virgin with Cherub.
The bell tower can be found close by and is one of the traditional points of reference in the northern area of the lagoon.