Philanthropist David Rubenstein, who has already donated tens of millions of dollars to refurbish the Washington Monument and other icons, is giving $18 million to fix up the Lincoln Memorial.

The National Park Service announced the gift Monday. The money will be used to fix the memorial's roof, clean the marble and improve accessibility by adding a second elevator. The park service also plans to create 15,000 square feet of visitor space tucked beneath the memorial for exhibits.

Rubenstein said his admiration for Lincoln drew him to this project.

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"Lincoln deserves to have his memorial in tip-top shape," he said in a phone interview.

The Lincoln Memorial draws more 7 million visitors annually and is the most visited attraction on the National Mall.

Park Service Director John Jarvis said the memorial, dedicated in 1922, is structurally sound but does need some repair work.

"It's pretty stout, and I think really has held up quite well for a structure of its age," Jarvis said. "But you can't build a 100-year roof."

The memorial is built on pilings, and the park service is going to explore ways for visitors to see the foundations that anchor the memorial to the bedrock. The unseen superstructure is marked with graffiti from the workers who built the memorial over a seven-year period, including caricatures of former President William Howard Taft and memorial architect Henry Bacon.

Rubenstein, a billionaire who founded The Carlyle Group investment firm in Washington, has already given $7.5 million to repair the Washington Monument after a 2011 earthquake, $5.4 million for the Iwo Jima Memorial in Arlington, Virginia, and $12.35 million for Arlington House, the home of Confederate Gen. Robert E. Lee on the grounds of Arlington National Cemetery.

Philanthropist David Rubenstein (L) tours the 'undercroft' of the Lincoln Memorial, February 15, 2016, in Washington, DC. Rubenstein announced he is giving $18 million to make improvements to the Lincoln Memorial. Drew Angerer, Getty Images

He said he hopes his donations have spurred others to think about giving.

Will Shafroth, president of the National Park Foundation, believes it has. He notes that donations to the foundation have grown from about $25 million three years ago to an expected $100 million in this fiscal year. On Monday, the foundation announced that a $350 million, five-year capital fundraising campaign begun in October 2013 is about half way to reaching its goal.

"Due to things like Mr. Rubenstein's generous gifts, we've tapped into a real vein of interest ... in highlighting the importance of these national treasures," Shafroth said.

Rubenstein, a history buff, said he is particularly excited that his gift will provide the park service a better opportunity to tell Lincoln's story to visitors at the memorial, and generally increase awareness about his presidency.

"It will be good if people read more about Lincoln and what he did to keep the country together," he said.