Less than people expect, and that is not a criticism. The interior is a single open bay with a brick floor, roof timbers overhead and a small amount of interpretation. There is no furnished scene, no recreated barricade and no waxworks. You walk in, stand in a room about the size of a double garage, and work out for yourself that twenty-odd people, some of them dying, spent a night and a morning in it.
Give it ten minutes, then give the next twenty to the John Brown Museum a short walk away on Shenandoah Street, which carries the narrative properly: the planning at the Kennedy farm, the raiders themselves, the trial, and what the country made of Brown afterwards.
Note the brickwork if you like that sort of thing. A building dismantled and rebuilt four times carries the evidence — mismatched courses, replacement brick, the cupola rebuilt more than once.
The building is open on the park's current conditions listing, which is not true of everything around it: the Civil War Museum, the Black Voices exhibit and the Harper House were all closed for repairs in late September 2026.