Auckland at it's narrowest is about 1 mile wide. This is from the Tamaki Estuary where it is crossed by Gt. South Road to the Manukau harbour at Otahuhu. At it's widest it about 12 miles from Bucklands beach to the Airport.
The narrowest point of Manhattan is the northern tip of it (the Washington Heights and Inwood neighborhoods) which sticks out like a finger pointing. This part of Manhattan is only about half a mile to two thirds of a mile wide. Manhattan is 2.3 miles wide at its widest point.
Manhattan is 2.3 miles (3.7 kilometers) wide at its widest point, and about 4000 feet (about three quarters of a mile) or 1219 meters (about 1.2 kilometers) wide at its narrowest point. It is 13.4 miles (21.6 kilometers) long.
"The cricoid cartilage is the narrowest point of the airway in children younger than 5 years of age; in adults, the narrowest point is the glottis." (Morgan, Mikhail, & Murray. Clinical Anesthesiology 4th ed. p. 924)