The Anchor Symbol
2nd or 3rd century
Crypt of the Church of Santa Cecilia in Trastevere, Rome
The anchor is an early symbol for Christ. The iota and theta to the left and right of the anchor are the first letters of the Greek words for "Jesus" and "God."
See also Crosses and Crucifixes
Photographed at the church by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.