Junius Bassus (ca. 317-359) was a high-ranking Roman official, who served in the Roman senate and held the office of "Praefectus Urbi" for Rome, more or less what we would consider as the office of the Mayor. As a politician from a prominent family, upon his death, he would have had a memorial bust displayed in a prominent public place, like in the Forum or along the Appian Way. Instead, his elaborately sculpted sarcophagus was his memorial, with scenes depicting stories from both the New and Old Testaments.
Although Emperor Constantine had signed the Edict of Milan in 312, which legally ended Christian persecution, Christians were still considered marginal members of Roman society, because their refusal to worship state deities was perceived as undermining and threatening to the state. In fact, for three centuries up until Constantine's conversion, Christians were among the most persecuted groups within the Roman Empire.
Even into the time of Bassus, many still believed it was not possible to be both emperor and a Christian. Proper Romans would have therefore concluded that it wasn't possible to both a prominent Roman politician and a Christian -- but that's precisely what Bassus appears to have been.
The cover to the sarcophagus described him as a neophyte, suggesting that he had converted to Christianity late in life or upon his deathbed; scholars suggest that he may have been practicing in secret throughout his life. In any case, the sarcophagus is historically important for two reasons:
It was the first public memorial of a prominent Roman to display Christian beliefs, and it is considered to be the finest example of Early Christian art. For a more detailed description of the artwork, read the links: