How does the water in the Huxin Pavilion of Prince Gong’s Mansion circulate only in but not out?

The water in the Huxin Pavilion of Prince Gong's Mansion can only go in but not out, because the water source of the Huxin Pavilion comes from Yuquan Lake, which is in line with the Feng Shui theory of making money. The fact that water can only enter but not exit may mean that water flows from the lake surface into the pavilion in the center of the lake, and no longer flows out of the pavilion. Instead, it is recycled through the drainage system in the pavilion or natural evaporation. This water circulation system was common in ancient garden architecture.

Please note that this is only a possible explanation. The specific water circulation method may require more in-depth research and understanding of the history and architectural structure of Prince Kung's Mansion to arrive at an accurate answer.