The Trust for the National Mall and the National Park Service announced Thursday an open design competition to re-imagine three derelict spaces on the Mall.

In the first phase of the competition, architects, landscape architects and others can submit a written prospectus describing how they would improve the following spaces:

Union Square — the area near the west front of the U.S. Capitol that includes the Grant Memorial and a circular pool. It’s right by the U.S. Botanic Garden.

Sylvan Theater grounds — the theater and storage areas in the slope southeast of the Washington Monument.

Constitution Gardens Lake — the water feature south of Constitution Avenue and 24th Street.

The question for all of the areas, said Caroline L. Cunningham, president of the trust, which advises and raises money for Mall projects, is how to make the areas more hospitable.

The competition project will be managed by Donald J. Stastny, an architect and urban designer and a former winner of the American Institute of Architects Thomas Jefferson Award for Public Architecture.

The process is scheduled for 36 weeks.

“In the first phase, we are looking for their design philosophy and experience. We don’t require sketches for any particular space,” said Cunningham. “We are interested in how they would treat the space and how they would approach the space.”

For the second phase, a jury will select 12 designers, who will put together a team and demonstrate to the committee that they can do a complicated project. For instance, Union Square has a tunnel underneath it.

In the final phase, judges will look at sketches and models and select a winner for each location. An announcement is expected May 3, Cunningham said.

The trust estimates that the Mall has not had a major renovation in 30 years, though work has started on the Reflecting Pool at the Lincoln Memorial, the front apron of the Jefferson Memorial and the D.C. War Memorial.

Total costs for the three projects will depend on the winning designs, said Cunningham, who added that the nonprofit trust, which was founded in 2007, has raised $9 million and leveraged $70 million in federal funds. All of the projects are a private-public partnership.

Former first lady Laura Bush has agreed to be honorary co-chair of the fundraising drive, Cunningham said.

Cunningham said she hopes that at least one of the projects will be completed by 2016.