Digging down for more urban underground space is imperative for the city's future development, according to senior officials.

"Beijing will need to have 200 million sq m of underground space. However, the current development and utilization process is backwards," said Li Changshuan, head of the Beijing Civil Defense Office.

Li said the current total area of underground space in the city is about 40 to 45 million sq m, which mainly includes previous bomb shelters, the basements of residential apartments and public buildings, as well as subways system.