Dove and olive branch
In Judaism, Christianity, and Islam an olive branch is a sign for peace. The Torah, The Old Testament and The Qur'an describe a story in which a dove was released by Noah after the Great Flood in order to find land. The dove came back carrying an olive branch in its beak, proof for Noah that the Great Flood had receded. (Book of Genesis 8:11).
Defeated Roman armies displayed olive branches as a white flag to indicate surrender.
The motif can also represent "hope for peace" and even a peace offering from one man to another, as in the phrase "extend an olive branch".
Peace dove graffiti in Madrid. The Castilian Spanish "paz" translates to "peace".
Photographer is Daniel Lobo, daquellamanera on flickr.com