燕子洞
- 网络swallow cave;swallow hole
燕子洞-
特类喀斯特洞穴旅游生命周期探讨&以云南建水燕子洞为例
A study on the life cycle of special karst cave with a case of Jianshui Swallow Cave in Yunnan Province
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燕子洞生命周期形成机制研究
Preliminary study of tourist cycle of swallow cave in Jianshui county
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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 a400m vertical shaft , deep enough to engulf the Empire State Building .