默兹河在林堡东部蜿蜒迂回，成为与荷兰林堡省的天然边界。

The river Maas meanders in the east - and forms the natural border with Dutch-Limburg.

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他们声称，纸浆工业会对乌拉圭与阿根廷之间的天然边界乌拉圭河(Uruguay River)造成污染，而且还会损害当地的旅游业。

They claimed that the industry would pollute the Uruguay River, the natural border between Uruguay and Argentina, and harm the local tourism industry.

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有些毫无意义，跨越了天然的地理边界和种族边界。

Many don't make sense, and many cut across natural geographic or ethnic lines that would easily suggest themselves.

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But when that's not true, then there is a typical sort of modern frontier, a land bridge which there a line is-a theoretical line is drawn through it, and on one side is one city, and the other side is another city.

但还不止这些天然边界,另外还有种边界形式,和现代国境线很类似,是由一座陆桥,分割出一条界线…假象的界线,界线的一边是一个城邦,另一边是另一个城邦

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