Crews are expected to finish unwrapping the orbiter late Friday.
The shuttle was covered in 16,000-square-feet of plastic shrink wrap.
This is the first time since November that anyone has seen Atlantis. Since then, the wrap has protected Atlantis for its move from Kennedy Space Center to the visitor complex.
The 90,000-square-foot attraction has been under construction for 15 months. It is set to open on June 29.