 From the 6th century onwards, stone-based structures become more common, while the earliest are from stone and brick arches found in Han Dynasty tombs.The Zhaozhou Bridge built from 595 to 605 AD is China's oldest extant stone bridge, as well as the world's oldest fully stone open-spandrel segmental arch bridge.The vocational trade of architect, craftsman, and engineer was not as highly respected in premodern Chinese society as the scholar-bureaucrats who were drafted into the government by the civil service examination system.