MINNEAPOLIS — Infrastructure design firm HNTB has signed a 15,187-square-foot office lease at 60 South Sixth, an office tower in downtown Minneapolis formerly known as RBC Plaza. KBS Real Estate Investment Trust III owns the 40-story, 710,332-square-foot property. Since purchasing the building in 2015, KBS has invested over $24 million in renovations. In 2022, KBS spent more than $6.5 million on the refurbishment of common areas and the fitness center. KBS also plans to add another tenant lounge. Brent Robertson and Andrea Leon of JLL represented KBS in the lease, while Eddie Rymer of JLL represented HNTB.