A quasi-celtic cross made of large symmetrical knot with a circle interlaced through its center.  The knot is made up of straight lines which are vertical, horizontal, or at 45° angles, and of circular arcs all of the same radius.  If the large circle were to be removed, then the over-under interlacing of the crossings of the horizontal and vertical lines at the center would have to be reversed to preserve the alternation of the knot interlace pattern (see <a href="//commons.wikimedia.org/wiki/File:Celtic-knot-cross_no_circle.svg" title="File:Celtic-knot-cross no circle.svg">Celtic-knot-cross no circle.svg</a>).
AnonMoos
Derived from the original PostScript vector source code (by AnonMoos) of <a href="//commons.wikimedia.org/wiki/File:Celtic-knot-basic-linear.svg" title="File:Celtic-knot-basic-linear.svg">Celtic-knot-basic-linear.svg</a><br>