原来，墨西哥的燕子洞有四百米深，足以放下整个帝国大厦！
The Cave of Swallows in Mexico is a 400m vertical shaft, deep enough to engulf the Empire State Building.
就这样燕子穿过洞来到屋里。
由于屋顶上有一个洞，燕子很容易进去。
It was easy enough to get in, as there was a hole in the roof.
由于屋顶上有一个洞，燕子很容易进去。
It was easy enough to get in, as there was a hole in the roof.
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