On Monday, a medical giant will begin building its mega-complex in New Haven.

The groundbreaking for the 11-story office building that will house Alexion Pharmaceuticals is scheduled to take place 10 a.m. Monday. The project is slated to finish in 2015 and is part of a larger Downtown Crossing project to connect New Haven with the Hill neighborhood, which is home to the Yale-New Haven hospital and the Yale Medical School. Alexion Pharmaceuticals was founded in New Haven and then moved its headquarters to Cheshire, Conn.

The Downtown Crossing project will also close exits 2 and 3 of the Route 34 expressway and replace the College Street Bridge.