An arena is a place where sports, entertainments, and other public events take place. It has seats around it where people sit and watch.
例句
...the largest indoor sports arena in the world.世界上最大的室内体育场
N-COUNT
活动领域;舞台
You can refer to a field of activity, especially one where there is a lot of conflict or action, as an arena of a particular kind.
例句
He made it clear he had no intention of withdrawing from the political arena...他清楚地表明他无意退出政治舞台。Oil speculation proved a natural arena for his skills.在石油业中进行投机活动对他来说游刃有余。