Sometimes not only church interiors but façades were also decorated with mosaics in Italy like in the case of the St Mark's Basilica in Venice (mainly from the 17th–19th centuries, but the oldest one from 1270–75, "The burial of St Mark in the first basilica"), the Cathedral of Orvieto (golden Gothic mosaics from the 14th century, many times redone) and the Basilica di San Frediano in Lucca (huge, striking golden mosaic representing the Ascension of Christ with the apostles below, designed by Berlinghiero Berlinghieri in the 13th century). The Cathedral of Spoleto is also decorated on the upper façade with a huge mosaic portraying the Blessing Christ (signed by one Solsternus from 1207).
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What was special about St Mark's Basilica in Venice?
façades were also decorated