高不可登

Explanation: Described as difficult to achieve. Also described one high above, makes difficult to reach. With the unattainable. " 　　Source: Han-Chen Lin, "as Cao and Wei Wendi book" Ju Fu Mo the defensive, to weigh with the wall, high non-registration. " Thesaurus:  be too high to reach, Height not Accessibility, Gao Yang indemnity, Gaocha the skies, alp admiration