  We analytically compute the observational appearance of an isotropically
emitting point source on a circular, equatorial orbit near the horizon of a
rapidly spinning black hole. The primary image moves on a vertical line
segment, in contrast to the primarily horizontal motion of the spinless case.
Secondary images, also on the vertical line, display a rich caustic structure.
If detected, this unique signature could serve as a "smoking gun" for a
high-spin black hole in nature.
