Luy Lâu
Luy Lâu or Leilou was the first capital of the Han commandery of Jiaozhi following its 111 submission during China's conquest of Nanyue. It was also the headquarters of the larger province of Jiaozhou and the center of China's maritime trade on the Gulf of Tonkin and South China Sea. The old citadel is at in Thuận Thành in the province of Bắc Ninh.
Luy Lâu became a major center for Buddhism in Vietnam. Although the Roman embassies probably arrived at the later capital Longbian, it may have been the earlier Luy Lâu that was the origin of Ptolemy's Cattigara.
