| 21. | These features were the last major natural obstacles that had to be crossed prior to reaching Beirut.
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| 22. | They see natural obstacles as a challenge and get very creative on how they challenge that obstacle.
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| 23. | In some maritime environments such a defence is given by natural obstacles, such as the Arctic ice shelf.
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| 24. | The challenge in the game comes almost completely in the form of natural obstacles in the cider factory.
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| 25. | Marshlands, other natural obstacles, and barricades made of stone, earth or timber provided defense at the kingdom's borders.
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| 26. | Because of its u-shape, the eastern side of the citadel was more vulnerable due to less natural obstacles.
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| 27. | It is crossed by three large rivers, but an international system of ferries helps cross these natural obstacles.
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| 28. | The marshland of the River Ribble and the Savick Brook were natural obstacles preventing easy access north-west of Preston.
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| 29. | A number of major roads link Jordan and Syria in this region, crossing undulating terrain with no natural obstacles.
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| 30. | It is a natural obstacle that separates the Shenandoah Valley and Cumberland Valley from the eastern part of Maryland.
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