  A walking droplet possesses fascinating properties due to its peculiar
wave/particle interaction. The self-propelling motion of such a droplet is
driven by the Faraday instability triggered around the droplet at each impact.
We studied in this article how such a droplet behaves in an annular cavity
where a periodic pattern is placed underneath the liquid-air interface,
altering the Faraday instability. We show that, while the annulus ensures a
circular motion of the droplet, the periodic pattern affects the global droplet
motion. Similarly to electromagnetic waves in photonic crystals, the average
droplet speed nearly vanishes when the pattern has a characteristic length
close to half the Faraday wavelength. This effect opens ways to design guides,
reflectors, lattices and metamaterials for such macroscopic particles.
