Audi Field, shown in a rendering, is built on an urban site that came with challenges. (Courtesy D.C. United)

When Audi Field opens in mid-July in Washington, a few blocks from Nationals Park, the $400 million project will establish another building block in the redevelopment of the District of Columbia’s inner core. For D.C. United, an original Major League Soccer franchise, it signals a rebirth for the team.

The 20,000-seat facility is situated at Buzzard Point, an urban neigh...