President Trump's renovation kick has now reached the Lincoln Memorial Reflecting Pool.

The president told reporters Thursday that his administration is planning to pour down a new surface onto the bottom of the pool, atop its stone flooring. The surface — made out of the "latest and greatest filament" — will be colored "American flag blue," he said.

Built in the 1920s, the Reflecting Pool and its surroundings were comprehensively renovated in 2012, paid for by $34 million in Obama-era stimulus funding. The National Park Service has carried out some renovations since then, and the pool is also periodically drained to scrub out algae, garbage, goose droppings and other detritus.

But during an Oval Office event on drug prices, Mr. Trump said he is disturbed by the "terrible" condition of the pool, a historic sight that featured heavily in Martin Luther King Jr.'s 1963 March on Washington and other major events at the Lincoln Memorial.

He estimated that renovating the pool will take about a week and cost roughly $1.5 million. He said contractors have begun working on the stones, and started laying down its new "industrial-grade" surface on Thursday.

"You're going to end up with a beautiful, beautiful reflecting pool, the way it's supposed to be," he said, showing photos of the construction process. "Much better than it ever was, actually."

Mr. Trump told reporters he drew inspiration for the project from his days as a New York real estate developer, during which he estimated that he built more than 100 swimming pools. He said it was "essentially a pool surface" and that he told one contractor to "think of it as a swimming pool." (The basin is more than 300,000 square feet and the length of about 12 Olympic-sized swimming pools.)

Tasked with choosing a color for the pool floor, Mr. Trump said an unspecified contractor talked him out of picking Bahamas-style turquoise, arguing "American flag blue" would look more appropriate.

Mr. Trump has pledged to deal with the Reflecting Pool in the past. In November, he posted to social media a video of garbage strewn next to the pool surface, writing: "Study it hard because you won't be seeing this Biden filth and incompetence much longer!"

Earlier this month, he wrote that he and Interior Secretary Doug Burgum will fix the pool "at a fraction of the cost" that the administration was initially quoted.

Since returning to the presidency last year, Mr. Trump has sought to put his stamp on major landmarks in the D.C. area, making changes large (tearing down the White House's East Wing to make way for a ballroom) and small (adding a "Presidential Walk of Fame" to the West Wing).

He has also proposed overhauling the Kennedy Center for the Performing Arts, building a gigantic triumphal arch across the Potomac River from the Lincoln Memorial and painting the Eisenhower Executive Office Building white.

Mr. Trump has pitched the renovation projects as a way to beautify the city and address long-overdue maintenance needs, and has argued that his planned White House ballroom will serve as a much-needed event space that can be used for state dinners and other functions.

But some of the projects have drawn criticism from preservation groups and congressional Democrats who argue that he is unilaterally changing — and in some cases, tearing down — iconic public spaces without sufficient input from Congress or the public.

The president has also faced criticism over the funding mechanism for the ballroom, paid for with hundreds of millions in private donations, and for a decision by the Kennedy Center's board last year to add Mr. Trump to the center's name.