Ictinus was a Greek architect, one of the most celebrated of Athens, known for his work on the Parthenon on the Acropolis, the Temple of the Mysteries at Eleusis, and the Temple of Apollo Epicurius at Bassae. According to Vitruvius (Ten Books on Architecture, preface to Book VII), Ictinus designed
One of the oldest Christograms is the Chi-Rho (☧). It consists of the superimposed Greek letters chi (Χ) and rho (Ρ), which are the first two letters of the Greek χριστός, 'Christ'. It was displayed on the labarum military standard used by Constantine I in 312 AD.