Mepphyland is an amusement park located outside of True Cross Academy. There are numerous statues in the likeness of Mephisto Pheles throughout the park as well many thrill rides typical of the average amusement park but with a theme seemingly based around Mephisto's whimsical tastes.
True Cross Academy arc
Mepphyland is first seen in both Chapter 9 of the Manga and in episode 12, A Game of Tag of the Anime. Rin Okumura and the Exwires are sent there to investigate and exorcise a Ghost that had been causing trouble at the park.  During their mission however, Amaimon attacks Rin, stealing Kurikara and taunting him into a frenzy.  He is eventually driven off by Shura Kirigakure whom was disguised as Yamada. He gave Kurikara back before making a hasty exit.  Great damage to the park is sustained as a result.