During the following decades, the city saw increased threats to its heritage. In 1964, the Ballarat City Council passed laws banning pillar-supported verandahs in the CBD, which threatened the removal of historic cast iron verandahs in the city. The by-law was met by staunch opposition from the National Trust, which had begun campaigning to protect some of the city's most historic buildings. By the 1970s, Ballarat began to officially recognise its substantial heritage, and the first heritage controls were recommended to ensure its preservation. With the opening of Sovereign Hill, the city made a rapid shift to become a major cultural tourist destination, visited by thousands each year.