Back in the day when the entire complex was open to everyone, a guy I worked with spent his spare time exploring the "blank" areas on the public blue prints of the Capitol. This comprises a lot of real estate.. He reported all sorts of interesting places, but one was particularly interesting. A door in the hall right outside of the Senate entrance to the public gallery, unlocked and unguarded, a stairway and at the top a door with two guards who escorted him out. He reasoned he had found the Intelligence Cme room. In those days, we didn't know who sat on that cmte, its location or schedule.

No tunnel to union Station. Wasn't one to the old library of congress but one was built from Cannon bldg to new Madison annex. Once I got lost in the garage and ended up in a park behind the Rayburn bldg. The exit was a small stone bldg I saw every day but assumed were gardener supply sheds. Now when they put the subway system in, I am sure the opportunity for new undetected digging was huge.