Keystone Property Acquires 880,000 SF Office Building in Philadelphia for $114M

PHILADELPHIA — Keystone Property Group has acquired One Washington Square, also known as the Penn Mutual Tower, located at 510-530 Walnut St. in Philadelphia. An undisclosed seller sold the 880,000-square-foot commercial building for $114 million. The building is occupied by several corporate headquarters, including the American Board of Internal Medicine, Urban Engineers and BPD International. Keystone plans to convert the building’s ground floor and mezzanine office space located at 530 Walnut St. into retail space.