It's always seemed like the world's two great builders, Man and Nature, have been involved in a millennia long struggle, desperately trying to one up the other. This 'match-up' has never really been declared but you know it exists. And in trying to get one over the other, their styles have often blurred. Here are a few structures that look they could have been made by either, or even both. Can you tell which is which? Go on, have a try.

1.

Source: MyWallpapers

2.

Source: Mapio

3.

Source: Wherecoolthingshappens

4.

Source: QualityVillasItaly

5.

Source: Tripfreakz

6.

Source: Wired

7.

Source: Topturkeytravel

8.

Source: Tumblr

9.

Source: Reddit

10.

Source: Swide

11.

Source: Tourismprofile

12.

Source: Thousandwonders

13.

Source: WallwideHD

14.

Source: Geolocation

15.

Source: Iliketowastemytime

16.

Source: Hotel-Plaza

17.

Source: Iliketowastemytime

18.

Source: Topgreenparadises

19.

Source: Wikipedia

20.

Source: Reddit

So, how many did you get right?