Traditional Pergola is made often from a structure of brick or stone pillars that support strong wooden beams and iron bars covered with climbing plants.
The Oriental differ pergolas very little of the traditional mode characterized by a combination of the horizontal with the vertical.
Because pergola to have an authentic oriental ends of the horizontal transeversale must be curved upwards. Rustic pergola has long been used in old gardens climbing roses. This structure is less resistant than other types and therefore you should use waterproof glue and galvanized nails when you combine items.
Second, you should fix reinforcing struts through vertical studs to large pergola stability.