The Qianlong Emperor's interest in the Xiyang Lou began and ended with water. Fountains were the chief attraction -- specifically, the mechanical water features that European courts used to demonstrate their mastery of engineering. Castiglione designed the buildings, but it was Benoist who solved the hydraulic challenges, creating China's first European-style water feature at the Xieqiqu complex in the southwest corner of the site. The fountain basins were shaped like crabapple and chrysanthemum flowers, fed by bronze waterspouts cast in the forms of animals -- rams, ducks, and fish. Water was pumped from a tower filled by a mule-drawn water wheel. The most famous fountain, at the Haiyan Tang, featured twelve bronze waterspouts with human bodies and animal heads representing the Chinese zodiac, each activated in sequence every two hours to form a water clock.

Among the most remarkable structures was the Huanghuazhen, a maze formed of 1.2-meter-high embossed brick walls stretching 1.6 kilometers in total length across an area of roughly 89 square meters. At its center sat a circular pavilion in the European style. According to tradition, the Qianlong Emperor would sit in this pavilion during the Mid-Autumn Festival and watch his concubines race through the labyrinth carrying yellow lanterns, their progress visible above the walls as bobbing points of light. The labyrinth was destroyed along with the rest of the complex in 1860 but was rebuilt during conservation work between 1977 and 1992 -- one of the few structures on the Old Summer Palace grounds to be restored.

The Fangwai Guan, a two-story mansion built in 1759, was decorated with European landscape paintings by the French Jesuit Jean Denis Attiret and by Castiglione himself. But its most intriguing association is with Consort Rong, a Uyghur woman in the Qianlong Emperor's favor, who is said to have frequented the mansion. The building reportedly contained tablets inscribed in Arabic, which were lost in the early 20th century. In a complex designed to showcase European aesthetics for a Chinese emperor, the presence of a Uyghur consort and Arabic inscriptions adds another layer to an already extraordinary cultural collision. The Fangwai Guan's ruins survive today -- broken walls that once held French paintings viewed by a Qing emperor's Uyghur companion, a story that no single cultural tradition can fully claim.

When Anglo-French forces set fire to the Old Summer Palace in October 1860 during the Second Opium War, the Xiyang Lou's stone and brick construction proved more durable than the mostly timber Chinese buildings elsewhere on the grounds. The masonry survived the flames, leaving the carved marble pillars, broken archways, and scattered stone blocks that visitors see today. These ruins are the most photographed features of the Old Summer Palace site, which has led to a widespread misconception that the entire Yuanmingyuan was European in design. In fact, the Xiyang Lou occupied only about 7 hectares in the northern part of the Garden of Eternal Spring -- a small fraction of the palace's total 3.5 square kilometers. Their survival is an accident of materials, not a reflection of their importance. But as ruins, they have become more eloquent than the buildings ever were, speaking simultaneously of ambition, destruction, and the strange beauty that remains when cultures collide and empires fall.