Watch Cineb. Former workers and locals recount the history of the Belfast Gasworks. Built on ground owned by the Marquis of Donegall and opened in 1822, the works generated heat and light for the city for more than a century and a half. So profitable were the works, the proceeds paid for Belfast City Hall. The gasworks continued as a vital source of domestic and industrial energy well into the twentieth century – by the end of World War II some 120,000 people were reliant on on the facility for their heat and light. By the 1960s, however, new technologies and energy sources began reducing public dependence on the works. Today the old funnel and clocktower mark the place that was once the heart of Belfast’s gas-making industry.