  We report on the realization of artificial ice using superconducting vortices
in geometrically frustrated pinning arrays. This vortex ice shows two unique
properties among artificial ice systems. The first comes from the possibility
to switch the array geometric frustration on/off through temperature
variations, which allows "freezing" and "melting" the vortex ice. The second is
that the depinning and dynamics of the frozen vortex ice are insensitive to
annealing, which implies that the ordered ground state is spontaneously
approached. The major role of thermal fluctuations and the strong vortex-vortex
interactions are at the origin of this unusual behavior.
