According to Genesis, Noah's Ark had a door in its side.
Genesis 6:16 describes the Ark's structure and says that its entrance was placed in the side. The verse also mentions an opening or roof and three decks, giving a compact description of the vessel's basic arrangement. The text does not call the entrance a ramp, staircase, or gatehouse.
The door becomes important later in the story. After Noah, his family, and the animals enter, Genesis says that the LORD shut them in. This wording gives the entrance a narrative role as well as a practical one: it marks the transition between the threatened world outside and the protected space within.
Illustrations often show a large hinged doorway reaching from the ground to an upper deck, but Genesis does not specify its exact shape, size, hinges, or method of operation. The canonical fact is simply that the Ark had one described door in its side.