In May 1924, dramatic events saw a police raid smash down the door. They were looking for Zhang Guotao and Gao Junyu, mentors of the May fourth Movement in 1919 and early leaders in China's communist movement. Gao, realizing the long arm of the law was out to get him, made good his escape, disguised as a cook, charcoal covering his face and carrying a food basket. He had no time to inform Zhang and his wife, Yang Zilie, who were not so lucky.

With no time to escape, they were arrested, tortured and imprisoned until October 1924. After release, Zhang rose to power within the Communist Party, and commanded the 4th Red Army on the Long March in 1935. It wasn't long before he fell into disgrace however, and he defected to the Kuomintang, ending his life in exile. Gao became secretary to Sun Yat-sen, but died in hospital of exhaustion at the age of 29 in 1925.

An iron door has replaced No. 16's wooden gate. Guo, a 50-year-old resident says the houses inside were reconstructed when a "break-down for new construction" project was launched in 2007. "The only original thing left is this main gate," Guo says, pointing to the broken-down gate. Only by its shabby appearance can we tell its real age and grandeur. Guo explains he had little knowledge about the former residents, until a steady stream of visitors arrived, enquiring after its history.

Resident in No. 16 since the 50s, 80-year-old Jia says that the gate used to have a wooden latch at the back, and a pair of stone lions on each side. It was smashed to pieces during the Cultural Revolution. "The siheyuan had two areas separated by an inner gate," says Jia. "Apart from two jujube trees the front yard was rather empty. The back yard had the houses where the residents lived." Today the inner gate and the trees are gone, some newly built houses replacing them, crowding the already limited space of the siheyuan and ruining its traditional layout.

Jia guessed that Gao and Zhang most likely lived in the back yard at the time of the raid. Later on, members of the air force lived there, he explained, but ordinary families soon replaced them after 1949. On the left side of No.16, a shabby red brick house is a 1970s era bomb shelter, sticking out like a sore thumb compared to the traditional look of the gate.