People standing under a large spherical mirror see the world inverted, hanging above them as a real image. The shape of this image world depends upon where on the floor the observer stands. In this paper formulas for calculating image positions as a function of observer position are derived and depicted in diagrams of typical image worlds. The images formed by light reflecting several times in the mirror are also calculated. There are both an erect real image world and doubled rings of inverted images surrounding the single-reflection image world.
E. Garmire, "Calculation of the Optical Effects of a 27.5-m Spherical Mirror," Appl. Opt. 10, 2760-2762 (1971)