what are Tang Dynasty's contributions?

I think the most important Tang Dynasty did to the Chinese history is its focusing on the intercultural communication between China and foreign countries. It not only bring the foreign culture into China, but also let foreign people know Chinese splendid culture.
Secondly, it is the peak time of Chinese poems which lasted for a long time. Nowadays, the Chinese students still learn those poems. The pattern of poems become an important literature pattern in Chinese history.
Thirdly, Chinese examination system became perfect in this period.