When you step out of the coolant on Keyes. That's my least favorite part of the game because it's so damn dark. Anxious to see how they light this area.
But I'm honestly most excited to see how the interior of the forerunner structures look, particularly about half of Assault on the Control Room, half of the shaft on Silent Cartographer, all of the Library, etc. Bungie did an amazing job with the pristine detail inside the halls of the Ark in Halo 3. I'm hoping we get something similar from Anniversary. What little bit of Forerunner steel I saw in the campaign demo has me hopeful.