What's that?

I'm off today so I was wasting time looking at Google Earth. I was looking at New Mexico because I lived there in the mid 1960's. Anyway I was looking at Carlsbad, to see if you could tell that there was a huge cave there, I couldn't. (click on pics)



Just to the east of there I noticed that there was an "I" someone had a question about what this is, but he was mostly interested in the square things. What blows my mind is the circular symbol with the North to South and West to East lines through it! I've seen that symbol a million times. Oh yeah, I lined the Google Earth pointer up on it and it is exactly North and South and East to West. (There's a path or road that cuts across it but you can tell that it's seperate from the original.) It's in an interesting place too, Carlsbad Caverns to the west, springs nearby and some kind of depression(?) to the East. If you want to look for yourself, it's @ 32 degrees 11' N and 104 degrees 17' W