The Old Wan Chai Post Office, the oldest surviving post office building in Hong Kong, is located at the junction of Wan Chai Gap Road and Queen’s Road East. Constructed in 1912-1913 and opened in 1915, this L-shaped building features a simple pitched roof with charming gable ends and mouldings. Declared a monument in 1990, it was converted into the "Wan Chai Environmental Resource Centre" in 1993. In 2024, after renovations, it was renamed “kNOw Carbon House,” continuing its legacy as a community landmark.