The Augmented Knight's Castle is an augmented toy environment that enriches the children's pretend play by using background music, sound effects, verbal commentary of toys, and different forms of tactile and visual feedback in reaction to the children's play. Moreover, interactive learning experiences can be integrated into the play (e.g. to teach songs and poems or to provide the child with facts about the Middle Ages). We describe the different possibilities that are realized in our augmented playset, based on various mobile and pervasive computing technologies. Radio frequency identification (RFID) technology is used to automatically and unobtrusively identify toys in the playset. Mobile phones and "smart toys" equipped with sensors and RFID readers are introduced into the playset to enhance the play and to provoke further interaction.