This article discusses a representation of the relationship between a child and a big city in American and European children’s and teens’ literature. In many books, a child or a teen is portrayed as a contemporary flâneur, an idle city walker. Following Eric Tribunella’s adaptation of Walter Benjamin’s definition of a flâneur to children, the article explores various book representations of the big cities as they are seen through the eyes of a child. The city dweller perceives her environment as an exciting, even though sometimes threatening, place. Acting as a flâneur and a voyeur, a child develops a complicated relationship with the streets and museums of the big city. Enormous walking (and transportation) possibilities of the city are very attractive for youngsters. The hidden wonders of the big city mesmerize the curious minds of children and teens, making them natural voyeurs. Children are capable of combining the aimless gaze of a flâneur with the precise attention of a voyeur. Often, a city becomes one of the very important characters in a book, and a child forms a partnership with the city. In spite of the notion of adults that the city is a dangerous place for children, children immensely enjoy the city spaces, streets, parks, and museums. Museums particularly work as symbolical places of safety and exploration. Contemporary children and teenagers enjoy even more freedom to be city flâneurs and voyeurs due to the newly acquired speed of movement, including the use of bikes, scooters, and public transportation. With the main focus on New York City as one of the most striking example of a big city in children’s books, the article also discusses the literary representations of other megalopolises and large cities, such as Moscow and Minsk.