Years ago, my congressman personally took me from his office in the Cannon building to the tunnel, and we rode the shuttle train to the Capitol.it was a very special visit to DC for me.
Back before 9/11 closed off a lot of access I was on a trip with a group in DC and I remember walking the tunnels under the capitol to the house and senate buildings. Some of the underground sections I walked were for service personnel and others who needed to move things around. Can’t do that any more but it was a lot of fun to explore.
I’ve also been in these tunnels, I didn’t know it was a secret.
We walked, I believe, from my congressman’s office to the Capital via an underground tunnel. We were on a guided tour. Had to go through security.
I got to stand on the Speaker’s balcony (Paul Ryan was speaker at the time) and take pictures. It was a blast.
Yes, there are lots of small halls, stairs, nooks, etc.