There were efforts over the years to maintain the structure, but no concerted effort existed until as recently as 1980 CE when the wall was made a priority of the Chinese government as a tourist attraction and source of revenue. It was not designated a UNESCO World Heritage Site until 1987 CE, but even with that designation the wall is slowly crumbling. Today, according to historians and preservationists who monitor the site, there are only about 600 miles (372 km) of the wall left in stable condition.