From Wikipedia,

The Tang Dynasty (Chinese: 唐朝; pinyin: Táng Cháo; Middle Chinese: dhɑng[1]) (18 June 618--4 June 907) was an imperial dynasty of China preceded by the Sui Dynasty and followed by the Five Dynasties and Ten Kingdoms Period. It was founded by the Li (李) family,

The Tang Dynasty, with its capital at Chang'an (present-day Xi'an), the most populous city in the world at the time, is regarded by historians as a high point in Chinese civilization — equal to or surpassing that of the earlier Han Dynasty — as well as a golden age of cosmopolitan culture.

Tang Dao is one of greatest invention in Tang dynasty.

here is two links that offer more information about Tang Dao.

http://thomaschen.freewebspace.com/custom.html

http://www.shadowofleaves.com/Chinese_Sword_History.htm (less info)