Brandywine Realty Trust and Drexel University's Schuylkill Yards megaproject is finally underway.

Leaders from Brandywine, Drexel and Philadelphia, including Mayor Jim Kenney, were on hand Wednesday morning to break ground on Drexel Square, the 1.3-acre public plaza that will serve as the first piece, and central gathering place, of Schuylkill Yards.

The construction of the square will take place simultaneously with the redevelopment of the Bulletin building at 3001 Market St., the October purchase that allowed the project to finally get started. Brandywine CEO Jerry Sweeney expects the 250K SF building to be ready either when Drexel Square is finished in late 2018 or a few months later, in early 2019.

The remaining bulk of the $3.5B project, starting with two towers at 2002 and 3025 John F. Kennedy Blvd., will not begin construction until 50% of the buildings are pre-leased, Sweeney told Bisnow.

"We're a capital institution, so we can self-finance projects if needed," Sweeney said in an interview. "Finance is important to us, but more important is the right design and tenants."

One such tenant that would allow for that to happen is Amazon and its HQ2, for which Schuylkill Yards is at the center of Philadelphia's pitch.

Regardless of if Amazon chooses Philly and/or Schuylkill Yards, Wednesday's groundbreaking kicks off Brandywine's national marketing campaign for potential tech, life science and other office tenants to lease space, starting with the Bulletin building. Sweeney said he is searching for a tech anchor tenant and a ground-floor retail tenant for the redevelopment.

Although Drexel owns the bulk of the property to be used for Schuylkill Yards, Brandywine owns some parcels and serves as the master developer. To flesh out its diverse vision of integrated tech, science, office and residential components, it has brought on Longfellow Real Estate Partners and the Gotham Organization as co-developers for its new construction components. All told, Sweeney expects Schuylkill Yards to comprise seven to 10 new buildings, but not much is set in stone.

"It's a master plan, so we can modulate the timeline and design," Sweeney said.

With its stated focus on innovation, one component Schuylkill Yards is sure to include is co-working, though Sweeney said he did not know what form or company that would incorporate.