An aerial view of the Portland Museum of Art’s campus at Congress, Free and High streets, with the Payson Building – the museum’s main exhibition space – at center-right and, to its left, the former Children’s Museum where the expansion plan is focused. Photo courtesy of the Portland Museum of Art

The Portland Museum of Art has launched an international design competition to select an architectural firm to oversee a major expansion of its downtown campus.

The museum announced plans in February to begin raising $85 million toward the project, which is likely to include construction of a six- or seven-story, 60,000-square-foot building on the site of the former Children’s Museum & Theatre of Maine, as well as some renovations to existing buildings.

Portland Museum of Art director Mark Bessire stands in the Payson Wing of the building. Ben McCanna/Staff Photographer

“We are excited to invite experts from around the world to internalize the goals of the PMA Blueprint and turn them into physical spaces that bring them to life,” museum director Mark Bessire said in a statement. “This is no easy task, as our communities have made their expectations clear for open and innovative spaces that enable a flexible range of programs, exhibitions, and art.”

The project’s completion is still four years away, but Wednesday’s announcement is a major step. The museum is working with a New York consulting firm, Dovetail Design Strategists, to select an architect. Companies have until July 1 to submit interest. From there, the museum will select up to four firms to develop a concept design for the project, which will be due in November and will be displayed publicly. A winning team will be selected in December.

Museum officials and board members have envisioned a building that, in addition to more than doubling the exhibition space, would be instantly recognizable on the Portland skyline, with a rooftop restaurant and sculpture park.

“The unique competition we have designed allows for the power of architecture and the potential of ideas to collide, creating a platform that will captivate the very best, diverse professionals and will ultimately turn the PMA’s vision into a built reality,” Dovetail Design Strategists President Susanna Sirefman said in a statement.

The museum has been planning for an expansion for many years, but those plans accelerated with the 2018 purchase of the building at 142 Free St., which formerly housed the Children’s Museum.

The new building will be built on that site and include a ground floor with free art galleries, classrooms and community space, and room on the remaining floors for an auditorium, traveling exhibitions, offices, an all-ages “makers space” and a photography center.

The museum’s campus also includes four other buildings: the McLellan House, the Sweat Memorial Galleries, the Clapp House and the Payson Building, whose signature arches face the intersection of Congress and High streets.

Museum officials project the addition will allow Portland to accommodate between 300,000 and 500,000 visitors every year to view a collection that includes impressionist masters like Monet and Renoir, Maine icons Winslow Homer, Andrew Wyeth and others; and more contemporary names like mixed-media artist David Driskell and photographer Nan Goldin.

The project also coincides with an ongoing overhaul of Congress Square, one of the city’s busiest areas, that includes a redesign of the intersection and of the park that sits directly across from the museum.