That stands for Chesapeake Bay Bridge Tunnel. The sights along this mega-structure are pretty much the last that I noted on our trip. The rest of the ride home was devoted to research for a project that I and a fellow student are doing for a 'friend of Endicott' (actually, for a homeless shelter).
We stopped at the little snack bar along the CBBT, and what a surprise! It has been completely rehabbed. It used to be grotty. Now it's splendiferous. However, the barely 4'-wide hallway to the restrooms is unchanged and at times non-navigable.