The whimsical turret was a favorite of 19th-century architects, who liked to cap their towers with a flourish inspired by one of the historic revival styles. But because thin, vertical structures weaken easily, many of Philadelphia's Victorian buildings have lost their tops, if not the entire tower.

That makes the clocktower attached to the Sterling Paper Co. building in Frankford a remarkable survivor. The tower, which rises about three stories above the squat brick factory, features a canopied dome that calls to mind the great baroque church spires of Eastern Europe, or maybe a pasha's tent somewhere in North Africa. The clock's four faces, decorated with Gothic numerals, are still visible on all sides. Given the building's substantial age, it's even more amazing that the weathervane perched on top of the pointed turret still tells you which way the wind is blowing.

The historical record is spotty, but preservationist Ben Leech has concluded  the factory at 2155 Castor Ave. was built around 1858. The immense structure was originally constructed for a rope manufacturer, the Schlichter Jute Cordage Works. The neighborhood must have been thinly settled at the time, because an early photo shows the pristine plant sitting by itself in a vast open field. In those days, the factory had two matching clock towers, each with its own pointed, baroque cupola.

Their ornate design stood in sharp contrast to the plainly functional three-story factory. They probably served as a communication tool to beckon workers to the site -- and to ensure they started their shifts on time, as few owned watches in those days. At the fourth level, the shaft of the clocktower narrows. The architects could have left the roof flat but instead gave it a curvaceous canopy that could have come from the pages of an Arabian Nights storybook. The canopies were built by the Warren-Ehret Co., a roofing specialist founded in 1852 in Philadelphia that's now in Maryland.

Even with just a single tower, the factory is a distinctive industrial landmark -- although, unfortunately, not a historically designated one. After sitting empty for some time, the building was acquired in 1978 by Sterling, which makes cardboard boxes. It is astonishing to approach the building from Aramingo Avenue, which is dominated by a concentration of featureless, big-box stores, and stumble upon such strongly detailed architecture.

A few years ago, the Mural Arts Program honored the clocktower by repainting the faded factory wall sign with its own mysterious message: "There is no clock when it's time to fly." Even though the clock hands no longer keep time, the tower's presence still binds today's Philadelphia to its great industrial past.