Arena

 is one of the Locations in the game The Metronomicon.

Summary
Upon beating Spider Eye, the Arena, as well as the first set of challenges, is unlocked. The Arena houses all the challenges - beating them will earn the player special equipment or Street Creds.

Defeating each of the 5 bosses will unlock a new set of challenges. Additionally, a set of challenges is unlocked upon unlocking the boss song in The Moon. This makes a total of 6 sets of 5 challenges, and the number of playable challenges available can also be extended by DLC song packs.