zenith

(a) Astronomy, ｟the[one’s] -｠ the point of the celestial sphere in the sky directly above the observer; the highest point reached by a given celestial body

(a) 天頂(天球上において、観測者の真上にある天球の点のこと)

(b) the sky; the heavens

(b) 天空

(c) the highest point of one’s fame, fortunes etc.; culminating point

(c) 頂点, 絶頂, 全盛, 極地

The sun was well past the zenith.
at the zenith of one's fame
be at one's zenith
attain[pass] its zenith
At the zenith of its power, Mongol Empire ruled about 25 percent of the land on the earth.