Last week the Trust for the National Mall announced a project to rehabilitate the Constitution Gardens. Pictured: a model of phase one of the rehabilitation design.

What is the nation’s most visited National Park? Yosemite? Yellowstone? The Grand Canyon? Nope. If you guessed the National Mall, you’d be right. Though it gets a whopping 29 million visitors a year, many Americans don’t actually realize that it’s part of the park service.

National Mall locations such as the Washington Monument have become symbolic of the United States, but lesser known Mall sites like Constitution Gardens, for example, are literally hiding in plain sight. The nonprofit Trust for the National Mall (TNM), in partnership with the National Park Service (NPS), however, is trying to change that.

Children stand next to a polluted pond in the Constitution Gardens.

Just announced last week is what TNM is calling its “first priority” project to elevate the gardens’ profile with a $160 million restoration plan. In the words of TNM’s Senior Project Director Teresa Durkin, the goal is to “finally realize the full potential of Constitution Gardens.”

Originally designed by Skidmore, Owings, and Merrill (SOM) during the late 1960s and early ‘70s as the major site in Washington, D.C., commemorating the American Bicentennial, Constitution Gardens was envisioned as a relaxing and contemplative space between monuments. Today, the 38-acre gardens south of Constitution Avenue offers a small lake and meandering paths linking the World War II Memorial, Vietnam Veterans Memorial, Lincoln Memorial, and the 1830s Lockkeeper’s House.

(Left) The Lockkeeper's House; (right) A ranger explains what the Mall looked like several decades ago.

But an original plan that proved unsustainable combined with decades of deferred maintenance have resulted in gardens that don’t live up to SOM’s intent -- poor soil quality can’t sustain lush plantings, the lake fills with sludge, and cracked and deteriorated pathways are inaccessible for people with limited mobility.

Part of realizing the gardens’ full potential includes moving and restoring the Lockkeeper’s House, which I reported on last December.

A cracked sidewalk near the information booth.

“That’s phase one,” says Durkin. For phase two, NPS and TNM selected Rogers Partners Architects + Urban Designers and PWP Landscape Architecture to collaborate on the design.

“We selected the design team specifically because they submitted the only proposal that respected the heritage of the site,” says Durkin. “They were the only team that wanted to respect the original SOM plan.”

Damaged sidewalks make the Gardens inaccessible for people with limited mobility.

“When we looked at SOM’s original design for Constitution Gardens,” says Rob Rogers, partner with Rogers Partners, “we noted that it was modern in spirit, which is embodied by an optimism and clarity of form. And then, looking at the current condition of the site, it seemed natural to base our design on realizing what was never realized. [...] The original SOM plan called for a building located near the lake where now there is a pathway leading to the World War II Memorial.”

A schematic featuring the glass-walled restaurant in the distance.

Rogers’ plan, then, for a new pavilion will be to locate it nearby, but within the context of the landscape. Described by Rogers Partners as a simple cantilevered box that will sit on a plaza 20 feet above the lake, the structure will house a glass-walled restaurant.

As for the lake itself, its basic shape will remain unchanged. But the lake today is only three feet deep, has a concrete bottom, and quickly fills with sludge, all of which contributes to poor water quality. Future plans include increasing the depth to 12 feet and planting the along the water’s edge with aquatic plants.

The gardens themselves will be transformed -- details of the design include a canopy of trees to provide an acoustic buffer along Constitution Avenue, extensive native plantings, and a storm water management plan.

The model showing the gardens from a 17th Street view.

Moving and restoring the Lockkeeper’s House as a gateway to the gardens is planned to be completed by August 2016 as part of the NPS centennial. As with the Lockkeeper’s House, the gardens project will be funded 100 percent through private donations raised by the Trust for the National Mall. The current plan is to complete work in phases, with the final phase completed as early as 2018 depending on funding.