Cameraphoto Arte, Venice; Art Resource, N.Y.

ON THE COVER: Empress Helena (at center, dressed in orange) oversees the excavations of Golgotha, in this ceiling roundel painted in about 1745 by Venetian artist Giambattista Tiepolo, for the ceiling of a Capuchin church in Castello, Italy, and now in the Accademia, in Venice. According to longstanding tradition, Constantine’s mother traveled from Rome to Jerusalem in search of the cross on which Jesus died. When she began digging, she uncovered not only the cross of Jesus, but the crosses belonging to the two thieves who were crucified at the same time. To determine which cross was Jesus’, she instructed her workers to touch the wood to a sick man (at lower left); when the man was miraculously healed, she knew she had found the true cross.

In “The True Cross: Separating Myth from History,” Jan Willem Drijvers traces the Helena legend to its source (but not to Helena).