The Vatican Necropolis is a Roman street lying under the floor of St Peter's. It is a cemetery road of the first and second centuries, lined with small brick family mausolea that still have their painted walls, their stucco ceilings and the names of the families cut over the doors. Most of the people buried in it were not Christians: freedmen, traders and imperial servants who bought a plot on a hillside outside the city. Their tombs carry peacocks, vines, and in one case a figure driving a chariot of the sun.
Constantine's builders cut the hillside away, filled the tombs with earth and set the first basilica on top. They took that on in order to put the altar directly over one particular grave. Excavations between 1939 and 1949 uncovered the street, a red wall, and beside it a second wall covered in scratched prayers. In a cavity in that wall were the bones of a man of sixty or seventy, wrapped in cloth of purple and gold. Who he was is still argued over, and the tour says so plainly.