Why the grass at the Super Bowl is perfect even though it's an indoor stadium

The playing surface inside University of Phoenix Stadium for Super Bowl 49 looks impeccable.

It's blindingly green.

This is natural grass, not the synthetic FieldTurf playing surfaces you see inside other indoor arenas across the NFL. While Phoenix Stadium does have a retractable roof, Tim Newcomb of Sports Illustrated reports, it's not large enough to let in the sort of sunlight you need to grow a two acre grass field.

To get around this problem, the stadium's designers made the field itself retractable. The field you see is actually a giant, 40-inch-deep tray that's on wheels. During the week, they roll it outside so it can get natural sunlight and grow properly.

On the Monday before the Super Bowl, the field was growing right outside the stadium:

On Wednesday, the stadium's operators wheeled it back inside to get it ready for the Super Bowl.

It slides right in:

Here's what the entire process looks like:

Here's the stadium from above on Super Bowl Sunday: