  Celestial holography expresses $\mathcal{S}$-matrix elements as correlators
in a CFT living on the night sky. Poincar\'e invariance imposes additional
selection rules on the allowed positions of operators. As a consequence,
$n$-point correlators are only supported on certain patches of the celestial
sphere, depending on the labeling of each operator as incoming/outgoing. Here
we initiate a study of the celestial geometry, examining the kinematic support
of celestial amplitudes for different crossing channels. We give simple
geometric rules for determining this support. For $n\ge 5$, we can view these
channels as tiling together to form a covering of the celestial sphere. Our
analysis serves as a stepping off point to better understand the analyticity of
celestial correlators and illuminate the connection between the 4D kinematic
and 2D CFT notions of crossing symmetry.
