I have always loved Gothic architecture and one of my favorite things about this style is how symbolism is used in buildings and interior embelishments. One of my favorite examples is the trefoil design that you see quite often.
The term "trefoil" is an ornamental foliation or cusping introduced in the heads of window-lights, tracery, panellings, etc., in which the center takes the form of a three-lobed leaf (formed from three partially-overlapping circles). One of the earliest examples is in the plate tracery at Winchester (1222 - 1235). The fourfold version of an architectural trefoil is referred to as quatrefoil.
A trefoil combined with an equilateral triangle was also a moderately common symbol of the Christian Trinity during the late Middle Ages in some parts of Europe. Two forms of this are shown below:
A dove, symbolic of the Holy Spirit, is sometimes depicted within the outlined form of the trefoil combined with a triangle.
Can you find the trefoils and quatrefoils in these photos?