The main characters follow a yellow brick road, a guiding light of sorts, to find the Wizard so he can provide them with what they desire most. The road, however, is not a lighthouse, just as the Emerald City is not truly green. Both are illusions. To enter the city the main characters must wear green glasses fixed on their heads. The Gatekeeper explains that if Dorothy and her friends "did not wear glasses, the splendor and glory of the Emerald City would blind them." He also explains that “even those who live in the City must wear glasses day and night”. This edict was issued by Oz “when the city was first built.” What the characters don't realize is that by being forced to wear green glasses, Oz controls how they perceive the world. Dorothy and her friends are enslaved by Oz as much as the Munchkins and Winkies were enslaved by witches. Oz is more deceptive because he tricks everyone into wanting to wear glasses to be "dazzled by the splendor of the wonderful City." The color green symbolizes the concept of success and vitality. In the Emerald City “everyone seems happy, contented and prosperous.” Baum uses the verb “seems” to suggest that this may be a false notion. When Dorothy leaves the Emerald City and takes off her green glasses she notices that the silk dress "is no longer green, but pure”.