The Tang Dynasty
The Tang dynasty came into power after a short living Sui dynasty re-united China into a single kingdom after the divisions that followed the Han dynasty. They ruled for almost 3 years (~600 to 900 AD).
Wu Zetian was the de-facto ruler of the Tang dynasty for almost a 100 years.
The empire was challenged, because of ambivalence in military matters, by the Tibetan empire which essentially took over Qinghai and Southern Xinjiang.
The Tang era is considered very good for arts and culture. Li Bai and Du Fu, two of the most famous poets of China, lived during the Tang era.
The An Lushan rebellion happened during the Tang era.
The Tang dynasty lasted until ~900 AD, followed by the "Five Dynasties" period.