WATERVILLE — The Colby College Museum of Art will be the largest art museum in Maine when the Alfond-Lunder Family Pavilion opens July 13, according to college officials.

The 26,000-square-foot pavilion, making up the fourth wing of the museum, is designed by Frederick Fisher and Partners Architects, based in Los Angeles.

The pavilion will create a gateway to the existing museum, serve as a beacon for visitors and add 10,000 square feet of exhibition space to the facility, according to the college.

The glass pavilion will become the main entrance to the museum and include a spacious lobby with a sculpture gallery and terrace, as well as exhibition galleries, classrooms, a conference room and staff offices.

A glass-enclosed stairwell will be installed with a monumental, three-story wall drawing by Sol LeWitt that will be visible to visitors arriving on the campus’ main thoroughfare.

“This new pavilion is conceived as a glass prism that will reflect its natural and architectural context in continuously changing images,” Fisher, the architect, said. “The reflecting nature of the glass expresses the theme that art provides the opportunity to reflect on life. This was central to the museum’s position as a beacon of creativity and innovation on campus.”

The pavilion’s upper floor will house the college’s art department, to include new studios for photography and fine art foundation classes, as well as faculty offices and a student lounge.

Inaugural exhibitions at the expanded museum will focus on the Lunder Collection, which includes historic, modern and contemporary American art valued at more than $100 million and donated to the college.

The pavilion is named in recognition of a gift from the Harold Alfond Foundation and the partnership and friendship between Alfond and Peter Lunder.

The Lunder Collection was announced as a gift in 2007. This year, Colby formally took possession of the collection, widely acknowledged as one of the most important holdings of American art ever assembled by private collectors, according to information from the college.

The Lunder Collection consists of more than 500 objects, 464 of which are by American masters such as John Singer Sargent, Mary Cassatt, Winslow Homer, Edward Hopper and Georgia O’Keeffe, as well as important contemporary American works.

The collection also features works by James McNeill Whistler, including paintings, watercolors, pastels, etchings and lithographs, as well as books, journals, photographs and archival materials related to the artist.

The museum’s existing collection ranges from Colonial-era portraits to contemporary works.

“Until now, our museum may have been something of an underappreciated gem, though not to our students, faculty and alumni and the citizens of Maine,” Colby President William D. Adams said.

“But now, as we celebrate the bicentennial of the college, we can look forward as never before to welcoming visitors from around the country and the world who are going to discover that our museum has risen toward the top in its field.”

Some galleries are open during construction and admission is free.

Hours are 10 a.m. to 5 p.m. Tuesday through Saturday and noon to 5 p.m. Sunday.