This type of bridge was originally designed to allow pedestrians to cross canals while allowing the passage of barges beneath. When constructed using the climbing ascent and descent this had the further advantage of not using space from the adjoining fields for approaches.
In formal garden design a moon bridge is placed so that it is reflected in still water. The high arch and its reflection form a circle, symbolizing the moon.
When made from stone this becomes a true arch bridge, requiring stone approaches for structural stability. Chinese moon bridge at the Summer Palace, Beijing..