The former Marine Police Headquarters was constructed in 1884, comprises a main building, a stable block and signal tower (commonly known as Round House). The compound has been occupied by the Marine Police since its establishment until 1997, except for the Japanese Occupation (1941-1945) when it was used as a base by the Japanese navy. The main building was originally a two-storey structure to which was added an extra storey in the 1920s. The south-east and south-west wings of the main building served as married quarters. During the Japanese Occupation Period, extensive underground tunnels were constructed beneath the lawn but after World War II, in view of public safety, these tunnels were blocked and the lawn was re-turfed. The Signal Tower is the most unique building within the compound and was constructed to provide time signals to ships in the harbour. Its use diminished in 1907 when the time ball apparatus was removed to Signal Hill. Being one of the four oldest surviving government buildings in Hong Kong, the former Marine Police Headquarters Compound was declared a monument in 1994.