Wrapped in gray paneling with ample windows, the exterior of the new four-story building … looks decidedly more modern than its hulking, brick neighbor, Ponce City Market. But inside, the rich wood floors and timber beams overhead reveal that this mixed-use property is like few others in metro Atlanta or the country. The building, known as 619 Ponce, was constructed entirely from timber grown in Georgia and manufactured by regional suppliers, using centuries-old techniques that are experiencing a revival as developers seek to reduce their environmental footprint. On Thursday, 619 Ponce officially opened its doors to the public in Atlanta’s bustling Old Fourth Ward neighborhood, just steps away from the Beltline. …The 619 Ponce building is made of mass timber, a catch-all term for a range of engineered wood materials with the strength to serve as a structure’s load-bearing bones, in place of the steel and concrete that are typically used in commercial buildings today.