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

那就罗马椭圆型露天竞技场了，基本合能场。

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

从露天场馆到封闭建筑转变，就可能追求门票收入开始。