Abstract. This paper examines the development of the idea of heaven in relation to the sphaera mundi - the sphere of the world - in medieval literature. The sphaera mundi is a model of the cosmos that at its most elementary is very simple indeed. At the centre of it is the earth, so small as to be virtually a dot in comparison to the whole or even to the smallest star. Earth is surrounded by the sea, which in turn is surrounded by air, as also air is surrounded by fire. Surrounding the fire is a sphere that 'bears' the moon, and around that sphere are others, like layers of an onion, bearing the other planets: Mercury, then Venus, the sun, Mars, Jupiter and Saturn. Then come the sphere bearing the fixed stars and, beyond it, one or more others. All these spheres together constitute the sphere of the world.