Monday is moving day for 250 lawyers and staff at a downtown Boston law firm that’s relocating to a more collaborative workspace in the Financial District..

Burns & Levinson is leaving its home of nearly three decades at 125 Summer St. and moving three blocks up the Rose Fitzgerald Kennedy Greenway to 125 High St.

Burns & Levinson signed a 15-year lease for 100,000 square feet in the 950,000-square-foot tower, which is owned by Tishman Speyer, in August 2018.

The new space consolidates the firm’s workspaces on two floors, compared with five floors at 125 Summer St., and provides a collaborative environment connected by a grand staircase.

Gensler served as interior architect for the build-out, part of an all-women-led project team that included Elaine Construction and art consultant Erdreich White Fine Art.