According to Genesis, Noah’s Ark had three levels or decks. Genesis 6:16 instructs Noah to make the Ark with lower, second, and third levels.
The same verse describes a window or opening and a door in the side of the vessel. It also says the Ark was to be covered with pitch inside and outside, helping make it watertight in the narrative.
The three-level design is one of the few interior details supplied by Genesis. The text does not provide a complete floor plan, room count, or exact dimensions for each deck.
Later illustrations often add stalls, cages, ramps, and elaborate compartments. Those features may be imaginative reconstructions, but they are not all specified in the biblical passage itself.