The history and symbolism of the Celtic cross vary by culture and religion. In Ireland, some believe that St. Patrick designed the first Celtic cross, distinguishing it from the Latin cross by making a circle around the intersection of the two lines to symbolise his dream of a united Ireland under Christianity. The circle is said to represent anything from the sun to a halo, God's undying love for man to the mystery of the crucifixion. The cross and circle are often adorned with Celtic knot work or pictorial scenes and are made out of various materials, from stone to metal. It's common to see the cross atop gravestones.
Draw a standard Latin cross by drawing a vertical line and a horizontal line that intersect. The horizontal line should intersect the vertical line on the upper third and be slightly shorter in length. I will be referring to these lines as the four "arms" of the cross.
Make the image two-dimensional by turning the single lines into rectangular columns at least two inches in width so that you have room to add artwork later. Many Celtic crosses are shown with the arms tapering inward to the centre for decorative effect.
Add the circle to the section of the cross where the two lines intersect. The circle should originate in the centre of the top arm, encircling the centre point back to the origin. Make the circle two dimensional as well, but do not allow the inner rim of the circle to touch the centre of the cross. If you are having trouble picturing the image, visit http://www.freeceltic.com/celtic-celtic%20crosses-00.html.
Add knot work or narrative scenes. Celtic knots come in varying patterns and styles, and implementing one of them is a matter of personal choice. For a short tutorial on the eight basic designs of Celtic knots, see the Resources section. Narrative scenes are often religious in nature, depicting things like battles, sacrifice and spiritual icons.
The first Celtic crosses were built out of wood and stone and were very large. Modern Celtic crosses are commonly smaller and used as pendants in jewellery or are carved into small rocks that you can carry in your pocket.