By Jared Ebersole in Video — 30 Mar 2026

Boston's Tallest Building Had a Problem Nobody Wanted to Say Out Loud

The former John Hancock Tower is one of Boston's cleanest architectural icons, but its early years were defined by falling glass, wind studies, lawsuits, and secret steel.

The strangest thing about Boston's tallest building is how calm it looks.

Stand in Copley Square and the former John Hancock Tower, now 200 Clarendon, reads as a perfect sheet of blue glass. It reflects Trinity Church, the Boston Public Library, the weather, the sky, and almost nothing about its own messy history.

That was not how the building entered the city.

Where it is

200 Clarendon Street, Boston, MA 02116.

Boston has never been a simple skyscraper city. New York and Chicago turned height into civic theater early; Boston kept a stronger attachment to scale, streets, brick, and institutional landmarks. By the time the John Hancock Mutual Life Insurance Company planned a new headquarters in the 1960s, the Prudential Tower had already changed the Back Bay skyline. Hancock wanted something just as ambitious, but cleaner: a headquarters that would feel modern without looking heavy.

Henry N. Cobb of I. M. Pei & Partners gave them a slim rhomboid wrapped in mirrored glass. The shape was elegant because it was almost too simple. No crown. No masonry. No ornament trying to flatter old Boston. Just a tall, reflective plane beside Copley Square.

The design also made the building unforgiving.

When the tower was under construction, glass began falling from the facade. These were not little chips. Reports described large panes weighing hundreds of pounds popping loose in high winds and crashing to the streets below. Police closed nearby areas when conditions were bad. The building's opening slipped for years. The budget climbed. The tower picked up the nickname that every developer would dread: the Plywood Palace, because so many missing panes were temporarily replaced with plywood.

The visual must have been humiliating. A building sold as a perfectly reflective corporate future was standing in one of Boston's most visible squares patched like a job site.

The glass failure was not a single unlucky pane. It was systemic. The facade used thousands of insulated glass units, and the problem was eventually traced to the way the window assembly handled movement, heat, and stress. The daily expansion and contraction inside the panels helped transmit force in ways the system could not tolerate. In 1973, the project team announced that more than 10,000 panes would be replaced.

That alone would have made the Hancock Tower a famous construction failure.

Then the wind story got worse.

To understand the building's behavior, engineers tested models in MIT's Wright Brothers Wind Tunnel. The issue was not just whether the windows could survive gusts. The tower itself moved and twisted in ways that demanded a deeper look. A tuned mass damper was added near the top of the building to reduce sway and make the upper floors more comfortable. Then, according to later accounts by engineers and architecture critics, analysis raised an even more alarming possibility: under certain wind conditions, the building's narrow profile could become a structural vulnerability.

The fix was not visible from Copley Square. About 1,500 tons of diagonal steel bracing were added inside the building. That is the part that makes the story feel unreal. Boston's most elegant glass tower needed a hidden skeleton after the fact.

It is also why the building became a legal story. Hancock sued parties involved in the design and construction, and much of the detailed record stayed out of public view for years. In a 1977 Architectural Record essay, William Marlin wrote that the public knew only part of what had happened, while the deeper facts remained protected by lawsuits and silence. The building stood finished, polished, and admired, while its true repair story remained partly behind closed doors.

That tension is the whole building.

Architecturally, 200 Clarendon worked. It is still New England's tallest skyscraper, and it has become one of Boston's defining shapes. Its mirrored sides do what Cobb intended: they make a very tall building feel thinner, lighter, and oddly deferential to the square around it. From some angles, it almost disappears into the weather.

Technically, it became a case study in how a beautiful idea can fail at the scale of materials, wind, contracts, and construction tolerances. A glass skin is not just an image. It is a mechanical system, exposed to heat, pressure, movement, vibration, sealant behavior, fabrication choices, and every messy condition a rendering leaves out.

The Hancock Tower survived because people found the problems and spent the money to fix them. That is less glamorous than the myth that it simply "almost fell over," but it is more interesting. The building did not fail as a concept. It failed as an assembly of real parts in real wind, and then it was rebuilt into the icon everyone recognizes now.

Today, the tower gives away almost none of that.

It stands there polished, reflective, and quiet, turning Boston's old stone landmarks into a blue mirror. The Plywood Palace became a postcard. The crisis became invisible.

That may be the most Boston ending possible: the scandal is still there, but only if you know where to look.