'Like eating an elephant': The quest to honour Crazy Horse
As parts of the USA mark Native American Day the BBC has been getting a close up look at the sculpture that could one day eclipse the faces of American presidents at Mount Rushmore.
For more than 60 years workers have been painstakingly carving the shape of Native American war leader Crazy Horse on a mountain in South Dakota.
If completed it is set to be the largest sculpture in the world - but there are decades of work left.
Some of the people involved spoke to BBC News about the mammoth project.