见所未见

Explanation: See never seen before. Describe something very rare. 　　Usage: Verb-object type; as object, attribute; used in conjunction with the unheard 　　Source: Han Yang Xiong "Fa Yan Yuan Qian": "Zhong Ni is also the Seventy of the Japanese do not smell the smell, see what is unseen, the article is also insufficient to carry on." 　　Examples: Many wonders, then ~, unheard of. (Mao Zedong, "Report on Peasant Movement in Hunan")