John Gill Commentary Nehemiah 2:15

"Then went I up in the night by the brook, and viewed the wall; and I turned back, and entered by the valley gate, and so returned." — Nehemiah 2:15 (ASV)

Then went I up in the night by the brook
The brook Kidron:

and viewed the wall ;
that was on that side:

and turned back ;
did not go quite round the wall, the way perhaps being obstructed with rubbish, and was unpassable or he had not time to do it:

and entered by the gate of the valley, and so returned ;
into the city, the same way he went out of it, (Nehemiah 2:13) .