roaming German Shepherd

[13582]

My German Shepherd, about two years old, has just recently(within the past month or two) begun roaming. He never before has left our farm. We have pigs and another dog(in a pen) at our place. The first time, we picked him up and put him in the pen with our other dog for a couple days, let him out, and he went back to the same place within 10 minutes. Picked him up again and put him in the pen for a week. Let him out, and the exact same thing happened. The place he has been going to is within a mile away but has never been lead there by one of us. There are some black labs there, but no females. Let him out once while we were working outside, and we saw him trotting down the field road, so back in the pen he went. He is a very good dog, has never growled, and loves to play. I would love to hear any suggestions on fixing this problem.