"We have been thinking about who's the 'I'," says Liang Junjian, co-director of the documentary. "Apart from the architecture itself, it also means everyone who's been involved with the Forbidden City. Over the course of 600 years, many people have exerted an influence when inheriting its culture."

These people featured in the documentary include not only the researchers and the craftsmen at the Palace Museum, but also truck drivers who help to deliver building materials to the site. Much of the work is done after nightfall, hence the palaces are sometimes even more lively after dark than during the day.

The documentary has also included many sequences of visitors donning traditional attire and taking photos in front of the palace. Liang points out that they are also promoting the Forbidden City and traditional culture. Either as tourists or restorers, Liang says, everyone seems to have connections with the Forbidden City, one way or another, and through the historical landmark and space, we can connect to the past and the future. Such awareness is also a theme that the creative team tries to convey in the documentary, he adds.

Serendipitous findings during renovation work have often become surreal moments that bring the past rushing into the present.

For instance, when examining the Hall of Mental Cultivation, inspectors found, inside a ventilation brick, a program brochure for a traditional Chinese opera performance.

The ventilation bricks are an ingenious design whereby carved holes in the bricks allow the inner wood pillars to be dehumidified and maintained. The yellowed paper scroll was sealed inside one such brick more than 100 years ago.

Like a long-hidden time capsule, its chance discovery revealed the pieces performed and names of the performers for an imperial celebration of Lunar New Year.

Experts point out in the documentary that the brochure is one of its kind in the Palace Museum collection, with a high reference value for the research of traditional Chinese opera and imperial festival celebrations.

The documentary also has valuable footage of wall paintings hidden underneath the roof of the Hall of Ancestral Worship.