"What’s that?" Langdon finally asked, having to yell. He felt like they were approaching an active volcano.

"Free Fall Tube," Kohler replied, his hollow voice cutting the air effortlessly. He offered no other explanation.

Langdon didn’t ask. He was exhausted, and Maximilian Kohler seemed disinterested in winning any hospitality awards. Langdon reminded himself why he was here. Illuminati. He assumed somewhere in this colossal facility was a body… a body branded with a symbol he had just flown 3,000 miles to see.

As they approached the end of the hall, the rumble became almost deafening, vibrating up through Langdon’s soles. They rounded the bend, and a viewing gallery appeared on the right. Four thick-paned portals were embedded in a curved wall, like windows in a submarine. Langdon stopped and looked through one of the holes.

Professor Robert Langdon had seen some strange things in his life, but this was the strangest. He blinked a few times, wondering if he was hallucinating. He was staring into an enormous circular chamber. Inside the chamber, floating as though weightless, were people. Three of them. One waved and did a somersault in midair.

My God, he thought. I’m in the land of Oz.

The floor of the room was a mesh grid, like a giant sheet of chicken wire. Visible beneath the grid was the metallic blur of a huge propeller.

"Free fall tube," Kohler said, stopping to wait for him. "Indoor skydiving. For stress relief. It’s a vertical wind tunnel."

Langdon looked on in amazement. One of the free fallers, an obese woman, maneuvered toward the window. She was being buffeted by the air currents but grinned and flashed Langdon the thumbs-up sign. Langdon smiled weakly and returned the gesture, wondering if she knew it was the ancient phallic symbol for masculine virility.