The temple of peace, in Rome. The doors were thrown open in times of war and closed in times of peace. Some think the two faces of this mythical deity allegorise Noah and his sons, who look back on the world before the Flood, and forwards on the world after the deluge had abated. This idea will do very well in poetry.
“Slavery was the hinge on which the gates of the temple of Janus turned” (in the American war). —The Times.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894