John Stubbs, an American historic preservationist, had flicked on his flashlight and was slowly ascending a darkened staircase inside the Forbidden City when he stopped at a dusty paneled wall etched with elegant lines of calligraphy.

“I didn’t even see this until yesterday, or two days ago!” exclaimed Mr. Stubbs, almost ecstatic, as he stood in the dank, musty air. The calligraphy was a poem by the 18th-century Qing dynasty emperor Qianlong, who built the room as part of an intended retirement compound, a private city within the Forbidden City.

For a few days last week Mr. Stubbs and colleagues from the World Monuments Fund rummaged around the restricted Qianlong Garden section and admitted that the experience left them a little giddy. The fund, a private, nonprofit New York-based preservation group, has just begun overseeing the renovation of the Qianlong section, a project that should be finished by 2016.

“For us, it is wonderful seeing it this way,” Henry Tzu Ng, executive vice president of the group, said during an informal tour last Wednesday, “before 10 years from now, when it is restored.”