Baby Land is a place that made a debut in the episode, "Hose Water". Most of the places here are references to popular kids and children's novels. Everything in this place is designed to make a baby happy, or a toddler even.
Baby Land is the place where all babies reside, while they are still young and in egg form. The place is filled with toys, animals, and activities for young ones to indulge in. It also appears to be the source of nursery rhymes, such as "There was an Old Woman who Lived in a Shoe". The very nature of the place is so fun, childish, and optimistic, that anyone who goes there will regress to a younger age and into egg form.
In Hose Water, after Cyborg and Starfire act too childish, they physically turn younger and regress to eggs, and get taken to Baby Land by the Stork. Robin, Beast Boy, and Raven then follow to save their friends. There, Beast Boy and Raven quickly find fun in a lot of the activities and also become eggs. Robin tries to resist for some time, but he sees some face painting, which causes him to regress to an egg as well. The episode ends with the Titans in egg form stuck in Baby Land.