Cultural relics authorities in northwest China's Shaanxi province have announced that they will build an open eco-museum for ancient terraces that could date back to over 250 years ago.

The Fengjiang Terrace and Yanping Terrace, or the Fengyan Terraces, were discovered during a nationwide cultural relics survey in 2009.

They cover a combined area of 12,000 mu (800 hectares) in Xuanwuo township, Hanyin county, said a statement from the provincial cultural relics bureau on Wednesday.

The terraces, constructed by migrants from the central province of Hunan during the Qing Dynasty in the 18th century, involve about 300 steps on mountain slopes about 500 meters to 650 meters above sea level, according to the statement.

They are the largest and best-preserved Qing terraces in the Qin-Ba mountainous region -- the boundary between north and south China, it added.

The provincial cultural relics bureau will work together with the local government of Ankang city, which administers Hanyin, to build an open museum to preserve the terraces as they are of great significance to the study of ancient farming, said Zhao Rong, head of the bureau.

The museum will be unusual in that it will feature no big buildings, as its major exhibit will be the terraces, Zhao said.

However, the cultural relics department does have to build supporting showrooms for displays on the history of the migrants and ancient farming culture, according to Zhao.

It is not clear when the museum will be completed.