12 / 13
Christ's Monogram
Though not a cross per se, the Chi-Rho (or Xi-Rho) monogram, also known as "Christ's Monogram," is one of the earliest Christograms. It is formed by superimposing the first two letters—xi and rho —of the Greek word ΧΡΙΣΤΟΣ (Christ) in such a way that the vertical stroke of the rho intersects the center of the xi.

© ustin Ennis-(CC BY 2.0)