The Celtic Knot
According to Wiki, this symbol was used around the 4th century in Persian ceramics. It has also been used on buildings and coins, and cut into stones. You can tie your necktie in a Celtic knot. People sometimes tattoo various versions of it on their body. It has appeared in the movie Charmed, The Lord of the Rings, and Hunger Games. The English rock band, Led Zeppelin, used the Celtic knot on the cover of their fourth album.
As for me, this is not a religious symbol because it predates various religions. The Trinity knot is part of the ancient Irish culture. It means that there is no beginning or end, and that life is eternal. (image by Mossy Tree)

