Map Mysteries - Latitude and Longitude

What is the feature located at each of these latitude and longitude coordinates?
Why is this feature important?
Is the feature natural or created by humans>
Why is the feature located where it is?

Latitude and Longitude:

29.98, 31.13
38, -123
43.09, -79.07
-33.85, 151.21
27.17, 78.04
19.84, -155.50
-17.925, 25.855
48.858, 2.294
51.47, 0