A few days later, archaeologists uncovered the foundation for a large bow window that Washington had installed at the rear of the house. During his presidency, according to historians, Washington would stand at this window and greet dignitaries and the public.

The excavation now starkly shows the world of Washington and his grand window and, six feet away, the world of Hercules and the other slaves.

"Here," said one man on the platform, pointing to the window, "the powerful."

Sweeping his finger over to point at the kitchen, "Here, the powerless."

African Americans visiting the site often are deeply affected.

George Peebles of Philadelphia was almost speechless as he looked over the maze of walls the other day.

"Wow," he said, shaking his head. "Wow. They buried the ugliness of slavery, and it's just being uncovered centuries later.

"It shows how our history as Africans was covered up. For sure. Literally buried. Now it's a historical thing. But back then, just the ugliness of it - that's what gets me."

It is, he said, "the real deal."

Warrington, who is African American and a member of the project's committee of historians, officials and community members, said the site made it possible to talk about identity in a personal way.

"So many of us grew up without a clue of who we were," she said. "It's not even something you can explain."

Looking at the site, she said, evoked "those people reaching up out of the soil, telling their story. It's a monument of what happened."

Cheryl Janifer LaRoche, a historical archaeologist, has spent many hours on the platform explaining to visitors what they are looking at.

"I love this view without the walls because it strips away a lot," she said the other day, surrounded by people on the platform. "I think about walls a lot. This walling away is so symbolic for this site. Now you see this small space between here [at the bow window] and there [at the kitchen] is the space between the great statesman working out his understandings of democracy and the people that he enslaved."

"Yes," said a woman, "and the people who were slaves were not too far away. But they had to come up to serve him."

People, black and white, craned their necks to get a better look.

LaRoche said discussions of race between blacks and whites were often impeded by a "guilt component" in whites and a "shame component" in blacks. But the viewing platform at the President's House has provided a way around such emotional blockage.

This dig "is creating a space - I don't want to say of comfort, that's not the right word - it's creating a space of possibility for discussion," LaRoche said. "It's an opportunity to touch a chord in the past, and it's an opportunity to touch a past that's been so maligned and hidden, buried and walled away. . . .

"What I am seeing is so vast, and the possibility of what I am seeing is so profound, I'm having trouble, in my mere mortal self, talking about it."