Standing on the glass balcony of the Willis Tower made my legs go weak. The cars below looked like ants, and the lake was a deep, endless blue. An older man was too afraid to step on it, so he squatted down and reached out to touch the glass, while a child next to him jumped around. Clouds drifted past the building, their shadows slowly moving across the city wall. When the elevator came down, my ears were ringing, and there was a long line in front of the ice cream stand outside.