Albert Barnes Commentary Nehemiah 3:16

"After him repaired Nehemiah the son of Azbuk, the ruler of half the district of Beth-zur, unto the place over against the sepulchres of David, and unto the pool that was made, and unto the house of the mighty men." — Nehemiah 3:16 (ASV)

Beth-zur – Now Beit-sur, on the road from Jerusalem to Hebron (Joshua 15:58).

“The sepulchres of David” should be understood as the burial place in which David and the kings, his descendants, to the time of Hezekiah, were interred. This was an excavation in the rock, in the near vicinity of the temple (Ezekiel 43:7–9), and on its western side. The position of this burial place was well known until the destruction of the city by Titus, but modern research has not yet discovered it.

The pool – Probably the pool made by Hezekiah in the Tyropoeon valley, west of the temple area.