庐山真面 — “The true features or actual state of something”

Mount Lu (Lushan), located in Jiujiang City, Jiangxi Province, is said to have gotten its name from Kuang Su, an eminent recluse during the King Wu of Zhou period, who built a simple dwelling (庐, lú) there. The mountain range is exceptionally grand, boasting clear waters and picturesque scenery, and is bordered by three rivers.

Due to its proximity to the rivers and its frequent shrouding in mist, it was often difficult for people to perceive its true appearance from different vantage points. The renowned Song Dynasty poet Su Shi beautifully captured this phenomenon in his famous poem "Inscription on Xilin Wall" (题西林壁): "From the side, a range; from the front, a peak. Far, near, high, low, no two views are alike. I cannot tell Lushan's true face, because I am myself in the mountain."

This idiom, "庐山真面," metaphorically refers to the actual facts or the true nature of something, drawing on the idea that one cannot fully grasp the truth when too deeply immersed or when viewed from a limited perspective.