Are you referring as the old Ground-Zero site in NM, aka Manhattan Project? That's cool that they open it up at all to the public. I was flying SAN-DTW a while back, window on the right side of the A/C and was looking towards the desert in the distance for it. Wish I had a GPS so I could gauge appx. how far the old blast area was. Not sure if there is any physical characteristics left after 60+ years anyway that you could see from the air.

Please report back as to how it went on your return. I, among others, have an interest in fissile things that go boom.