Beyond Xi'an's ancient walls stands a modern marvel, a 100-meter air-purifying giant, cnow recognized as the world's largest purification tower. This silent sentinel is already transforming skies in one of China's most polluted cities.     Home to 8.7 million, Xi'an's coal-dependent winters once meant mask-clad citizens and hazardous smog. But this solar-powered innovation changes everything. Functioning like a massive chimney, it:     1) Sucks in ground-level pollution   2) Heats air in solar greenhouses   3) Filters toxins through advanced systems   4) Releases clean air from its summit     The results? 10 million cubic meters of daily clean air, improving a 10 km² zone.  During peak pollution, smog levels drop from hazardous to moderate—with PM2.5 concentrations cut by 15%.  A breath of fresh air, literally.