The building's long axis and its largest single artifact: a full-size Saturn V, horizontal, the five F-1 engines at the west doors and the Apollo capsule - suddenly, comically small - at the east. The stages are separated so the walk passes through the gaps: 111 meters, stem to stern, and the walk itself is the exhibit. Scale dawns on the visitor somewhere around the second stage. The hall runs beneath the Jefferson Room rotunda, whose suspended F-1 nozzle is this hall's deliberate echo one floor up; the Rocket Revolution gallery (VII) opens onto the hall at its midpoint. Everything the museum says about the 300-year differential is measurable here: the distance from the Hearth Vault's campfire to this machine is one staircase and three centuries.