Zenith

an Arab word meaning literally the line of the head,--the point in the heavens directly over the head of the observer. No two observers have the same zenith. A line passing from the zenith through the observer's feet and through the center of the earth would pass through the corresponding node or point in the heavens directly opposite the zenith. This is called the nadir. Milton thus describes the fall of Satan:

As the zenith is the highest point in the heavens, it is taken figuratively to indicate the highest point in other matters, as the zenith of one's hopes, the zenith of prosperity. Duluth has been dubbed the "Zenith City."