noun (n)

• a sloping gallery with seats for spectators (as in an operating room or theater)(noun.artifact)

  Synonym:
  amphitheatre
  

  source: wordnet30
• an oval large stadium with tiers of seats; an arena in which contests and spectacles are held(noun.artifact)

  Synonym:
  amphitheatre, coliseum
  

  source: wordnet30
• An oval or circular building with rising tiers of seats about an open space called the arena.(noun)

  source: webster1913