The Guardian of the Gates is a character in several of the Oz books. He is never known by any other name, but he is depicted as a singular character who lives in a small room, based on its description significantly larger than a standard guardhouse, in the wall that surrounds the Emerald City. In The Wonderful Wizard of Oz (1900) and The Marvelous Land of Oz (1904), his job is to adorn green spectacle glasses around the heads of all visitors to the Emerald City before they enter. It is claimed that this is done to protect their eyes from the thousands of glittering green gems within the city that are so precious and rare, they would cause blindness without the spectacles. In fact Oz is "no more green than any other city" and it is yet another "humbug" created by the Wizard. The glasses can only be unlocked by a solid gold key that the Guardian always wears on a thick gold chain around his neck.