That must be the oval unroofed amphitheater in Rome. It was basically a stadium with comprehensive functions.

那就是罗马的椭圆型竞，基本上是综合能的体育。

The change from the unroofed stadiums to sealed off buildings maybe the beginning that tickets were sought.

从馆到封闭的建筑的转变，就可能是追求门票收入的开始。