The church of Santa Maria della Croce in Casaranello (Casarano, Italy, 6th century) is an important paleo-Byzantine testimony in Southern Italy. The building is well preserved and corresponds more or less to its original structure because in the late-medieval age the community of Casaranum decided to move the residential area up the hill overlooking the original hamlet. The German art historian Arthur Haseloff (1872-1955) visited the church in 1907, intrigued by a bibliographic indication by Wladimir De Gruneisen, and he found it in the miserable condition of stall for sheep and goats. When he entered the church, he immediately realised he was in front of one of the most important jewels of the paleochristian art: a treasure fallen into oblivion and whose value deserved to be highlighted. Haseloff summarily analysed the site of Casaranello, paying particular attention to the mosaic. This research promoted a new awareness towards Santa Maria della Croce and laid the basis for the restoration interventions carried out during the second half of the ‘900s. In particular, the restoration and preservation interventions performed between 1971 and 1979 outlined new guidelines for the study of the building and its artistic heritage. In 2018 the writer of this essay published a new interpretation of the mosaic of Casaranello for the Esperidi Editions. In 2020, with Alessandro De Marco, first for Christian-Albrechts-Universität of Kiel (Germany), then for the Edizioni Universitarie Romane, he completed this research with further historical, architectural and artistic notes on the entire building. An unknown figure, depicted in fresco, has been identified as the emperor Constantine the Great, while the mosaic revealed its symbolic message: a cathartic journey of the soul <i>per aspera ad astra</i>.