The bridge and the tunnel are, after all, inextricably linked. Whereas one on a bridge can be blissfully unaware, those in the tunnel never all. Often you aren't submerged into the tunnel but arrive there, possibly because a bridge must cross above you. Yet the tunnel exists as something submerging; you are physically blinded by the submerging of your body. Shrouded is another word.
In the corniest terms imaginable, you aren't always aware of yourself when you're up (unless the view is astonishing), but always uncomfortably aware of how submerged in darkness (the underbelly, even) you are when you're down.
The striking thing about this particular tunnel (context below) is that the Polish architects were so able to encapsulate the European street as a main artery of the property, much as a street of this design is a main artery of the city. The steps running down one side are carbon copies of those located in many European streets on a slight slant. The cobblestone hearkens back to a bygone era.
In totality, this property has become a microcosm of a city in a most triumphant way. Even more so than what will soon be the tallest building in the world, a self-proclaimed "entire city." Incroyable. Hats off to the Poles.