The building is clad in lustrous bronze panels that shift in color as they catch the sun's slow trek across the sky. Inside, a skylight shoots brilliant beams into a grand interior space.
But the two men hadn't traveled to Midtown Manhattan to look at the structure's famous features.
Instead, they slid their curious fingers along the pocked surface of the alloyed bronze facade. Inside, their hands explored a smooth, round railing of warm cherry wood, a counterpoint to the chilly glass panels of the main staircase. Their canes clicked along the intricate floor, sensing the shift from swaths of concrete to planks of Ruby Lake fir.
"We were exploring how we could sense it with a cane, sense it with our fingers, sense it with our feet," said Northern California architect Christopher Downey. "There is this great palette of textures. . . . All of a sudden, it starts to engage your brain in a different way."
Downey said he and Lisbon's Carlos Mourão Pereira joke that their meeting three months ago was the "first-ever International Blind Architects Conference."
But the questions that engage the men are deeply serious: What makes a building beautiful if you can't see it, and how can you create beautiful structures if you're blind?
For the last 22 months -- since Downey lost his vision after surgery to remove a brain tumor -- the 47-year-old has searched for answers to both queries, along with many others.
In spring 2007, Downey was coaching his son's Little League team when he began to have trouble following the ball. By that December, he could no longer play catch on his quiet, leafy street in suburban Piedmont.
"Even with just a simple, soft toss," Downey said, "I was just guessing at where the ball was."
That year's end was a busy time. Downey was leaving the firm he and a partner had opened four years earlier for a job as managing principal at Michelle Kaufmann Designs in Oakland, which specialized in green, modular houses.
A neighborhood optometrist could find nothing wrong with his eyes and referred him to a specialist. Downey visited ophthalmologists and nerve specialists. He had eye exams, was prescribed eye drops and eventually had an MRI.
Then, in February, Downey was called in for more tests. As he waited for results, he noticed "a lot of somber-looking doctor types" looking at his medical charts.
He was told that a slow-growing brain tumor was pushing on his optic nerves.
"I was given the names of surgeons and advised to see them as soon as possible," Downey said.
Surgery -- all 9 1/2 hours of it -- took place March 17, 2008, a Monday morning. The benign growth was deep inside his brain, close to the pituitary gland.
"The best tumor," he said, "in the worst spot."
The next day, Downey's vision was blurry, as predicted, and he couldn't discern his wife Rosa's brown eyes or her dark, curly hair. But he could make out colors and shapes.
A day later, though, the world appeared cut in half, as if a line had been drawn across his field of vision. Above the line was the same blurry, post-surgical vista. Below, darkness.