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

那罗马的椭圆型露天竞技场了，基本上综合能的体育场。

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

从露天场馆到封闭的建筑的转，能追求门票收入的开始。