Synonyms for Arena (same or very similar meaning)
WordNet sense 1 (a particular environment or walk of life):
area, domain, field, orbit, sphereWordNet sense 2 (a large structure for open-air sports or entertainments):
bowl, stadium, sports stadiumWordNet sense 3 (a playing field where sports events take place):
scene of actionFrom the ODE community, based on WordNetadd/edit