The Infinite Corridor is MIT's spinal cord. Many of the departments, classrooms, and labs radiate from there. Whatever you do, stay to the right when traveling the corridor and note that pedestrian speed increases dramatically when classes let out. One-sixth of a mile long, the Infinite Corridor is the backbone of a subterranean system connecting labs, classrooms, fishbowls, offices, and libraries. Jack Florey told me it was the third longest tunnel system in the world, after the corridors of the Kremlin and the Pentagon.