Those old trees, also referred to as "living cultural relics", have witnessed all kinds of changes in Beijing over the past centuries. Chao Yang, a senior researcher at Beijing Institute of Landscape Architecture, is one of the "doctors" who regularly do physical examination for all old trees in Beijing by means of B-mode ultrasound to avoid cavities in them. Chao Yang and his colleagues have always attached great importance to the protection of over 40,000 old trees in Beijing which are commonly regarded as symbols of Beijing's history and culture.

(Flavor of Beijing series is presented by the Information Office of the People's Government of Beijing Municipality and produced by Beijing Radio & Television Station.)