Aerial rendering of the Smithsonian plan to reimagine the museums and gardens along the southern edge of the National Mall.

At the first public opportunity to comment on the Smithsonian’s plan to reimagine the area around its iconic Castle, more than 80 people offered ideas, ranging from emotional pleas to preserve Haupt Garden to questions about how the institution will pay for the project.

Smithsonian employees, staff from the National Capital Planning Commission and architects from Bjarke Ingels Group gathered Tuesday in the red-stone administration building for the start of a 45-day public comment period. The meeting, required by the National Environmental Policy Act and the National Historic Preservation Act, allowed the Smithsonian to outline its preferred design – the $2 billion proposal unveiled last month by Ingels – as well as three alternatives.

The preferred version, which could take as long as 20 years to complete, includes long-delayed renovations to the administration building (known as the Castle), as well as the addition of two underground levels of visitor amenities, including a cafe, a store, an auditorium and restrooms. The new spaces would connect to the S. Dillon Ripley Center, the Arthur M. Sackler Gallery and the National Museum of African Art, which are underground. In addition, the Sackler and African Art Museum would get new mall-facing entrances, making it easier for visitors to find them.

Many in the audience seemed skeptical of the project and worried that its modern design would destroy the beautiful Victorian garden behind the Castle.

“I love the Victorian garden,” Smithsonian employee Russell Cashdollar said to applause from the audience. “Surrounded by the Arts and Industries Building and the Castle, it is perfection. It is a national treasure.”

Ann Trowbridge, the Smithsonian’s associate director of facilities and master planning who served as the program’s emcee, said the details about the garden – its exact design, the type of plantings it will feature, and more – have yet to be decided.

“If we don’t have a spectacular garden at the end of this project, we will not have been successful,” she said.

As required by law, the Smithsonian offered three variations of its plan. The first would include only basic repair and maintenance to the Castle’s mechanical systems. That alternative is meant to serve as a baseline to compare the effects of the other versions.

The second option – described as offering “minimal improvements” – includes replacing the Castle’s mechanical infrastructure and providing some seismic upgrades and renovations to the historic building. It would also repair the garden roof of the underground Sackler and African Art Museum galleries, but not dramatically improve the visibility of their entrances or connect them to the Castle and other buildings.

The third option closely resembles the Smithsonian’s preferred choice, but it does not include the sloping garden roof that would allow for visitors in the new underground space to see views of the expanded garden. It also does not include new gallery space for the Hirshhorn Museum.

Trowbridge said that the Smithsonian is not asking members of the public to choose the design they like, but instead to comment on the ideas outlined in all of them.

“We welcome all comments, not just about one (alternative) or the other,” she said. “We are looking for feedback.”

While the potential loss of the contemplative garden was a recurring theme, several members of the audience questioned the need to connect the various facilities. Alex Liebowitz asked what the institution meant by “improving access.” “The hidden agenda here, or maybe not so hidden, is they don’t think the Sackler and African Art Museum get enough visitors,” he said after the two-hour session ended. “They think if you have a more visible entrance, maybe they will attract more people.”

Judy Scott Feldman, president of the National Coalition to Save Our Mall, asked officials to consider their plan in the context of the entire Mall and to not turn their backs on that important public space.

“I’m all for comprehensive planning,” Feldman said. “The design seems introspective … and concerned with the buildings to the south of the Mall but not really looking north. Can you open up the options to include the mall itself?”

Trowbridge said that with about 70 percent of visitors coming from the Mall, that was not an issue.

“We are always oriented to the mall,” she said.

The public has until Jan. 30 to submit comments via the website that the Smithsonian has created for the project (www.southmallcampus.si.edu) or by writing to the institution. The Smithsonian and the National Capital Planning Commission will use the feedback to focus their analysis of the project — from its effects on traffic and storm-water management to views and visitor experiences.

An environmental assessment will be made public in the spring, giving people a second opportunity to comment on the project. The Smithsonian would like to present a final plan to the NCPC for approval next fall. Although some of the smaller components might begin shortly, major construction on the Castle is not expected to begin until 2021 at the earliest.