When On Google Earth?, No. 2.1

The anonymous winner of round 2 has failed to materialize by the deadline, so I offer When On Google Earth?, No. 2.1


What are we looking at, and when was the major period of occupation?
Post your attempts at an answer in the comments, and the first right answer gets to host ‘When on Google Earth #3!



Never mind what's down here. The otherwise unknown PDD answered correctly, but failed to reappear

Post your attempts at an answer in the comments, and the first right answer gets to host ‘When on Google Earth #3!

Over at Electric Archaeology Shawn has initiated a game called "When on Google Earth". As the winner of round one, I get to host ‘When on Google Earth #2.

So here it is:



What are we looking at, and when was the major period of occupation?

Post your attempts at an answer in the comments, and the first right answer gets to host ‘When on Google Earth #3!