The Moses Bridge in Halsteren, Netherlands.
It was originally the defensive moat of a 17th century fortress.
After falling into disrepair it had been recently restored, but designers thought it would be inappropriate to go against the original design and build bridges over the moats.
Instead, they came up with an 'invisible' bridge that sits within the moat and would allow people to cross virtually undetected from water level.
Via: @hypebeast