According to Genesis, God set a rainbow in the clouds after the Flood.
Genesis 9 presents the rainbow as the sign of God’s covenant with Noah, his descendants, and every living creature. The covenant promises that a flood will not again destroy all life on earth in the same way.
The passage describes the rainbow appearing in the clouds and says that God will remember the covenant when it is seen. In the biblical story, it therefore functions as a visible reminder of a promise, not merely as a weather observation.
The rainbow belongs to the covenant scene after Noah leaves the Ark. It is not described as an object inside the Ark, and Genesis does not call it a physical structure built by Noah.