[publius911]

I believe that the "hideaways" are a special perk of long term senators who have reached leadership positions, separate from their official offices, where no one may intrude.
They are literally called hideaways.

I can't recall whether they are all in one building or if they are scattered around the D.C.Capitol/mall area.

[Thank You Rush]

I’ve heard/read about the same thing. I thought they were in the actual Capitol building but I was wrong. I should have known better as that’s why they go back and forth on the underground trains...to/from building to Capitol. Well, anyway, I still wish her hideaway was in a deep cave somewhere in Montana.

“”In addition to housing the individual offices of each U.S. Representative and Senator, the Congressional Office Buildings have committee hearing rooms, staff rooms, multiple cafeterias, and are connected to the Capitol by means of several underground trains known as the Capitol Subway System.

The three Senate office buildings are along Constitution Avenue north of the Capitol:

Russell Senate Office Building (RSOB, completed 1908)
Dirksen Senate Office Building (DSOB, completed 1958)
Hart Senate Office Building (HSOB, completed 1982)””

https://www.tripadvisor.com/ShowUserReviews-g28970-d564560-r223453880-Senate_and_House_Office_Buildings-Washington_DC_District_of_Columbia.html#