The pagoda is the large Japanese style building that sticks up way higher than anywhere else in the area, you reach the second level with ninja run then you will see red lanterns around the edge that you can jump up to, ascending to the next level. It's several levels up, just aim your jump at the middle of the lamp, aiming at the line holding the lamp will make sure you don't jump over it. Once on top just chop up the only thing thats up there and the achievement will pop.