Cao Wei works as a guide at China Science and Technology Museum. [Photo by Li Zhushan/For China Daily]

"Lilac flowers typically have four petals, so if you can find five-petal lilac flowers, you find happiness. The participants were amazed to find two-, three-, five-, six-, and up to nine-petal flowers in the temple," says Cao.

Cao, grew up at the China Science Publishing House, which was previously the mansion of Prince Fu, Emperor Kang Xi's fourteenth son, and as a result has strong feelings about Beijing's heritage.

In the 1970s, Beijing was not as developed as it is today. It had a much smaller population and almost no high-rises. And, once in a while, herdsmen could be seen on Changan Street herding sheep.

Then, young Cao and his friends used to climb the roofs of the mansion on rainy days.

Cao attended a middle school that was located in Donghuamen Street, close to the Forbidden City. And, in the afternoons, Cao and his classmates would ride their bicycles to the Meridian Gate of the Forbidden City to play soccer beside the moat.

These memories of old Beijing prompted Cao to try and share the charm of the ancient capital's history with others.

Besides, in the 1970s, the China Science Publishing House was populated by people who were well-versed with cutting-edge science and technology.