The Palace of Lasting Happiness is easily recognizable because it’s an unfinished building in western style that contrasts sharply with all of those around it.
The original building burned down in 1845, and in 1909 the decision was taken to replace it with a "crystal palace", with glass walls similar to those of an aquarium, and fish swimming inside them. Each of the four corners of the palace was to be connected with a three-storey hexagonal pavilion.
As you can see, the construction has a metal framework, and the whole building is in white marble on the outside, with porcelain tiles on the inside. The building project was abandoned due to the exorbitant costs involved and the palace remained unfinished.