Capitol Hill is a neighborhood in Washington, D.C., located in both the Northeast and Southeast quadrants. It is bounded by 14th Street SE & NE, F Street NE, Southeast Boulevard SE, and South Capitol Street SE. From Wikipedia
In Season 22, Episode 18, Hanna leaves lobbying to rejoin fieldwork, delivers updates on Callen, Anna, and Tennant, and hints at Hetty Lange's location in a DMZ.