Dirksen/Hart Office Building
121 Constitution Avenue NE, Washington, DC
100% positive
Directions: Across from Dirksen 157 on first floor. Corridor is a little hard to find; if you're in the in the middle of Hart by Mountains and Clouds sculpture, walk towards Dirksen through the middle corridor, and after Capitol Building displays there's a corridor on your right. Bathrooms on the left.
Comments: Totally public but you will have to go through security to get into the building (food/drink fine, suitcases fine, packages, knives, weapons not fine). Male and female single-person bathrooms.