The Old Mental Hospital, or what remains of it, is a handsome 2-storey granite structure built in 1892. It is known for its Victorian architectural style with grand arch verandas and ornamented railings. It was used as the dormitory for the European nursing staff of the civilian hospital. It was also rumored to have been used as a prison and execution hall by the Japanese during World War II. It was later converted into a psychiatric hospital.
When the Castle Peak Mental Hospital opened in 1961, the Old Mental Hospital became a day treatment centre for psychiatric out-patients before being abandoned in the 1970s.
The building fell into disrepair and became the haunt of teenage ghost hunters and drug addicts. It was badly ruined by two fires, believed to be inadvertently started by trespassers. The destruction of the historic building prompted the government to take efforts in preserving and restoring what was left of it.
In 2001, everything except the north façade of the Old Mental Hospital was demolished and a new modern building was built on the site to house the Sai Ying Pun Community Complex. The new building also contains offices of charity organizations, dormitories for single people as well as social welfare facilities.
Considered as the only structure of its kind in Hong Kong, the Antiquities and Monuments Office declared the building a Grade I Historic Building in 1992. It is part of the Central and Western Heritage Trail.