  We report on the experimental realization of a Kapitza pendulum for ultracold
atoms. Using time-periodic attractive and repulsive Gaussian potentials, we
create an effective trap for ultracold neutral atoms in a regime where the time
average of the potential is equal to zero. We analyze the role of experimental
imperfections, the stability of the trapped atomic cloud, and the magnitude of
the effective potential. We find good agreement with the high-frequency
expansion of the underlying system dynamics. Our experimental approach opens up
new possibilities to study Floquet systems of neutral atoms.
