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露天竞技场了, 基本上是综合功能的体育场.
《简明英汉词典》
The wind unroofed the barn.
风掀掉了谷仓的顶.
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At that night, the strong wind unroofed the barn and a dog barked.
那天夜里, 狂风掀翻了谷仓的顶,狗儿也吠叫起来.
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In 7 th century BC, Romans inherited the traditions of Greece and built racetracks and unroofed amphitheaters.
公元前七世纪时罗马人继承希腊传统,就修建了赛马场和露天竞技场.
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"an unroofed shed"