Lively terra cotta dormers and ornaments decorate the steeply pitched mansard roof of the former Pittsburgh Union Trust Building, above which rise two chapel-like mechanical towers. The interior is organized around a central rotunda capped by a stained-glass dome. This building was built on the site of Pittsburgh's nineteenth-century Catholic cathedral. The architect, Frederick Osterling, was one of Pittsburgh's premier architects, and also designed the Arrott Building (1901-02), and the County Mortuary (1901-03). It was built between 1915 and 1917 and is now known as Two Mellon Bank Center.