If you load the dynamic map ...
http://70.176.220.199:8123
You'll see a chunk of the map that sticks out like a boner to the north.
If you look around the area where the shaft meets the body (explored area of the map), you'll see a large cobblestone patio built on a mountain ... that's my last location.
1. trace the tip of the boner, to the body of the map
2. keep going straight down until you see a cobble patio built into a mountain