Why does a pyramid face north?

The Great Pyramid's north-south axis is aligned to within three-sixtieths of a degree of true north-south. It would be worthwhile to note that this alignment is more accurate than that of the Meridian Building at the Greenwich Observatory in London, which deviates from true north by nine-sixtieths of a degree. Even though there is no evidence in ancient texts that the Egyptians used astronomical knowledge in the construction of the pyramids, it seemed possible that they did indeed possess such knowledge, and had used it in finding the true north.