Beijing, Shanghai, Shenzhen
The most visited and generally the safest for solo travelers. CCTV cameras are everywhere, police presence is high, and tourist areas have English signage. You can walk in most neighborhoods at night without issues. The main risks are tourist-targeted scams (see below) and pickpockets in crowded spots like Wangfujing or the Bund promenade. Metro and Didi are safe to use any time of day.