Based on the clue 'at its opening this nyc building was the largest m...', what is the answer?

Based on the clue 'at its mouth the gulf of sidra stretches 280 miles...', what is the answer? Based on the clue 'at its narrowest point this strait separates europ...', what is the answer? Based on the clue 'at its north end the dead sea receives this river', what is the answer? Based on the clue 'at its northern end this colorful sea branches int...', what is the answer? Based on the clue 'at its peak attila the huns empire ranged from the...', what is the answer? Based on the clue 'at its peak the ottoman empire stretched as far so...', what is the answer? What is associated with: at its peak this network endorsed by dionne warwick had 1500 mediums answering phones giving a… Based on the clue 'at its peak this standard oilers personal fortune ...', what is the answer?