Apartment rents have leveled off in Boston according to recent industry research, but that isn’t stopping developers’ plans for more multifamily projects in the downtown area.

The latest proposal would replace a small parking lot at 47-55 LaGrange St. with a 21-story, 157,000-square-foot tower.

Developer QMG LaGrange LLC of Boston, led by Steve Goodman, John Matteson and Fan Du, said the project will include large light sculptures hanging above LaGrange and Tamworth streets and lighted sidewalks in front of the building.

Designed by Boston-based architects Stantec, the building was inspired by the look of a cast-iron Chinese garden lantern, according to a project notification form filed this week with the Boston Planning and Development Agency.

“The façade design takes its cues from the dark-colored garden lantern’s material palette, cladding the building in a curtain wall system with intricate metal details. Sophisticated window opening patterns are developed to simulate the ornamental skin of a lantern,” the document states.

Plans call for 20 parking spaces. Because residential uses are proposed on the ground floor, the project would need a conditional use permit from the Boston Board of Appeal, according to the filing. The 240-foot-tall structure also requires waivers to exceed the maximum floor area ratio on the 8,759-square-foot parcel, and to exceed the 155-foot maximum building height in the Midtown Cultural District.

To comply with the city’s inclusionary development policy, 13 percent of the units on-site would be income-restricted.

QMG LaGrange hopes to begin construction by year’s end with completion in late 2019.