The Moses Bridge

A series of moats and fortresses were built over the West Brabant Water Line region of the Netherlands during the 17th century in order to provide protection from invasion by France and Spain. Fort de Roovere was surrounded with a shallow moat that was too deep to march across, and too shallow for boats.
From afar, the Moses Bridge is invisible to the eye. The flow of the moat appears continuous, as the water level remains at the same level. As visitors approach the fort, the bridge appears as a break in the water with its sloping walls containing it.