Although they only spent two weeks filming in the Black Hills, the actors and filmmakers of "National Treasure: Book of Secrets," say they were deeply affected by their experiences in South Dakota.

"The Black Hills are very unique," Nicolas Cage said in a news release authored by Disney Studios. "They were very, very special because it's Native American sacred ground. I found it uniquely beautiful and still something of a secret. I don't think people realize how beautiful that is in our own backyard."

Cage said it was awe inspiring.

"It definitely inspired the performances, being in those places. It gave us all a little boost," he said.

Just as the movie's filming in Washington, D.C., was a plunge into the nation's past, South Dakota took the company back even further, to its pre-contact, Native American roots, which figure prominently in the story of the film, director Jon Turteltaub said.

"With all of the amazing places we went to, the least likely suspect became our favorite," he said. "We all fell in love with South Dakota. It's spectacularly beautiful, the people were gentle and embracing, and there's an enormous amount of culture there."

Turteltaub said the past is very present in South Dakota, and by going to and shooting at Mount Rushmore, the filmmakers and actors started to feel much more about what the stone was before it was carved into American faces and what meaning the landscape had for Native people.

"We tried, as best we could in small ways, to start letting that seep into the storytelling and the moviemaking," he said.

Gerard Baker, the first Native American superintendent at Mount Rushmore National Memorial, along with the late Darrell Martin, assistant chief of interpretation at Mount Rushmore National Memorial, performed a traditional Indian blessing ceremony for the film crew - including stars Nicolas Cage, Jon Voight, Diane Kruger and Justin Bartha - before the camera first rolled at Mount Rushmore on the morning of April 20.

Martin, a member of the Gros Ventre Tribe of Montana was noted for his kindness and vast historical knowledge. He died unexpectedly the following week.

"National Treasure: Book of Secrets" was to be the first major feature film to shoot an important sequence at Mount Rushmore since Alfred Hitchcock brought Cary Grant, Eva Marie Saint and the "North By Northwest" production crew to the Black Hills for just two days in September 1958.

The film crew used Rapid City as a base of operations and filmed on a wide range of locations, with a full week's work not only at Mount Rushmore, but also at nearby Sylvan Lake in Custer State Park.

"I loved South Dakota," Helen Mirren said. "I loved the people, the landscape and the wildlife. It's a really extraordinary part of the world. When we were there, we were looking at each other saying: 'Do you realize how lucky we are? Isn't this the best job in the world, to be here in this incredible landscape shooting a fun film?'"