Simon Property Group will add to an already substantial Washington real estate portfolio if it’s counter bid with Farallon Capital Management for the financially troubled Mills Corp. is successful.

The potential merger would give real estate trust Simon purview over at least 10 Washington-area malls. Chevy Chase-based Mills owns five shopping malls in the Washington region, including Potomac Mills in Prince William County, while Simon owns the Fashion Centre at Pentagon City, the Leesburg Premium Outlets and other retail locations.