Oh if only I had the time and the ability. . . I was just looking at a text called the Ngự đề Danh thắng đồ hội thi tập (御題名勝圖繪詩集). This text was published in the 1840s, and consists of pictures, and poetry which emperor Thiệu Trị composed about each picture.
Some of the pictures are about the imperial palace in Hue, such as the picture here. This a picture of Minh Viễn Tower, which no longer exists.
This text is not unknown. You can find it mentioned on the Internet. However, no one has ever looked at it critically. There is a great way in which this could be done.
Philippe Forêt wrote a wonderful book entitled Mapping Chengde: The Qing Landscape Enterprise in which he talked about the Qing Dynasty’s imperial residence at Chengde and examined all of the meanings of the structures there.
The same could be done for Hue by using this text. The Nguyễn built Hue to make a statement. What was that statement?
The answer lies, among other places, in the arcane poetry which Thiệu Trị composed for this 900+ page text.