Cargo Bay 2 was the hold aboard the USS Voyager that first held Kes's airponics garden and, from 2374, the Borg regeneration alcoves used by Seven of Nine and later the rescued Borg children.
In the first season Kes converts part of the bay into an airponics garden to supplement the ship's food supply, as established in Parallax.
The space changes character in Scorpion, Part II, when the Borg working with Janeway against Species 8472 install alcoves and assimilate part of the deck. After the alliance collapses, the equipment stays. Seven of Nine recovers there in The Gift and from then on regenerates in the bay, which serves as her quarters.
In the sixth season Icheb, Mezoti and the twins Azan and Rebi join her there after Collective. Many of Seven's most private scenes are set among the alcoves, including the Borg Queen's intrusions in Dark Frontier and Unimatrix Zero.