"Quo vadis?" is Latin for "where are you going?", which according to legend was the question Peter asked of Christ as Peter fled Nero's persecution of Christians in Rome. Christ's answer was, "I am coming to be crucified again."
Peter interpreted this as a rebuke to his fleeing, and returned to Rome to accept martyrdom by crucifixion, reportedly upside down in deference to Christ's own crucifixion.
Henryk Sienkiewicz wrote a classic Polish novel by the name "Quo Vadis?" in 1895, describing the early persecution of Christians in Rome, and this novel later became a major Hollywood motion picture.