Not all the symbols in the National Cathedral are Christian symbols per se. The entire building seems to be telling the story of our nation. There are state flags hanging and state seals embedded in the floor. It is interesting to find such things as the 'space window.' Many of the friezes seem not to be religious at all, but rather historical. One I would reference is the stone carving of the signing of the Magna Carta. The wall hangings have various images of unusual things, many that I did not recognize as religious, though there seem to be many historical symbols in them.