In Genesis, Noah had to make a window for the Ark one cubit high.
Genesis 6:16 lists several construction features: the Ark was to have a window, a door in its side, and lower, second, and third decks. English translations differ slightly in how they phrase the window instruction, but the measurement of one cubit is traditionally associated with the window or opening.
The passage does not provide a complete architectural blueprint. It gives dimensions, materials, compartments, an entrance, decks, and the window while leaving many practical details unspecified. Later illustrations therefore make design choices that cannot be confirmed from the biblical text.
The window should not be confused with the Ark’s door. Genesis mentions both separately, and the door is said to be placed in the side of the vessel. The window later becomes important when Noah sends out the raven and dove to assess whether the floodwaters have receded.