The long association between Christianity and the flat-earth theory begins in the sixth century when a Greek monk of Alexandria, Cosmas, who had traveled widely in the East, retired to a cloister in Sinai and wrote his Christian Topography. In it he refuted the 'false and heathen' notion that the earth is a sphere, and showed that it is really a rectangular plane arched over by the firmament which separates us from heaven. The inhabited earth, with Jerusalem at its hub, is at the centre of the plane, and it is surrounded by oceans beyond which lies Adam's paradise. The sun revolves round a north polar mountain, circling its peak in summer and its base in winter.