Heritage conservation in Hong Kong is supposed to be pre-emptive and coordinated. Yet none of that happened when residents near what is known as Bishop Hill in Shek Kip Mei stumbled upon a magnificent sight , a forest of Romanesque pillars and arches unearthed by a demolition crew working for the Water Supplies Department. The 100 brick and stone structures within a circular wall were what remained of a long-disused underground reservoir built in 1904, but had failed to catch the attention of authorities as being worthy of preservation. Locals’ quick thinking and a social media blitz that sparked an outcry stopped destruction just in time and the Antiquities and Monuments Office is now doing the investigative work it should have carried out years ago. It is a mystery how the structure could have escaped the notice of heritage officials. Anyone seeing images of it is impressed by the construction, which has echoes of the aqueducts of ancient Rome. Architects are quick to point out the connection and that the technology and engineering are directly descended from those techniques of more than a millennium ago. That so perfect an example exists in Hong Kong is itself a wonder; the thought that no one in the government was aware of its existence despite the protective measures for heritage in place is disturbing. Workmen demolishing the reservoir so the site could be handed to the Lands Department had already torn down four of the pillars when locals intervened. The project has been halted and Commissioner for Heritage Ivanhoe Chang Chi-ho has apologised for the oversight and miscommunication . Officials had previously decided against investigating after being told by water works engineers that it was merely “a tank”. But architectural plans clearly show it is a sophisticated structure of impressive dimensions; questions are rightfully being asked as to how that went unnoticed and approval given for its removal. Hong Kong’s limited land for urban use and historical and political circumstances meant its built past was for decades bulldozed to make way for bigger and more modern structures. Only with wealth and a sense of belonging, particularly since the city’s return to Chinese sovereignty in 1997, has there been a conscious effort to preserve significant buildings and places. But while the government has a strategy for preservation and an impressive list of graded and protected sites, the reservoir debacle shows that the system is not infallible. Alert residents stepped in just in time. If the reservoir is considered structurally sound, it should be preserved. It can get a new lease of life through adaptive reuse, perhaps as a museum, cafe or art gallery. The incident has to serve as a lesson for those entrusted with protecting our heritage.