Well, I don,t think it's a tower, a compass or a helipad ( the helos are catered for 735 meters to the south east)

I can't say for sure, but being where it is on the tarmac, in front of what looks like HQ, it may be a painted emblem or crest.

The number 13 is used quite a lot when it comes to "Stars within a Sun" as depicted in a lot of US emblems and logo's. FBI, Department of Justice etc, for instance. (look up 13 stars in a circle, George Washington)

The way the tarmac has been cleaned up around where this object is indicates to me that it is a recent addition and possibly for something important.

I wonder where Air Force One parks up when it visits ?