DAKAR, Senegal-In a symbolic visit to Goree Island, President Obama today toured the departure point where African slaves were once forced to leave their homeland, bound and shackled for America and other foreign lands.

Stepping out alone into the "Door Of No Return" at the Slave House, the United States' first African-American president paused to scan the horizon. Moments later, he was joined by the first lady and the two stood side-by-side in the open doorway that drops sharply to the water's edge.

Credit: Evan Vucci/AP Photo

"It's a very powerful moment," the president later told reporters, "to be able to come here and to fully appreciate the magnitude of the slave trade, to get a sense in a very intimate way of the incredible inhumanity and hardship that people faced before they made the Middle Passage and that crossing."

The president said his visit serves as a reminder "that we have to remain vigilant when it comes to the defense of people's human rights - because I'm a firm believer that humanity is fundamentally good, but it's only good when good people stand up for what's right. And this is a testament to when we're not vigilant in defense of what's right, what can happen."

"It's always powerful for me to visit countries outside of the United States generally, but obviously for an African American, and an African American president to be able to visit this site I think gives me even greater motivation in terms of the defense of human rights around the world," he said.

The first family was warmly greeted by the islanders, who sang, danced and cheered as the president approached. Several in the crowd waved American and Senegalese flags and some wore t-shirts with Obama's face printed on them. The president, dressed casually in a white shirt, khakis, and sunglasses, spent several minutes shaking hands and posing for pictures.

The locals had been eagerly anticipating Obama's visit. Asked why they were excited for him to come, one woman exclaimed "because he is black!"

"We are proud for him to be the president of the United States," she told ABC News' Jonathan Karl. "Everybody is happy for him to come to Africa."

Obama is the third U.S. president to visit Goree Island. Bill Clinton visited in 1995 and George W. Bush came in 2003.

With reporting by ABC News' Jonathan Karl and Stephanie Smith