When it was first proposed in the 1970s, the 790-foot Hancock Tower was met with fierce resistance by residents who feared it would wreck the historic ambience of Back Bay’s Copley Square. In a stroke of genius, architect I. M. Pei covered the outside of the building with reflective glass, thereby enhancing rather than overshadowing the architectural beauty of Trinity Church, the Boston Public Library, and other nearby buildings.

Not everything ended happily, however—due to a design flaw, many of the 10,344 panes of glass began falling out and shattering on the sidewalk below before the building was completed. Pei later corrected the technique for hanging the glass (which he also used on the pyramid for the Louvre) and Hancock Tower is now one of the most striking in the city skyline. The observation deck on the 60th floor was closed to the public due to security concerns after 2001, and is only opened for special events.

Nearby, the much smaller “old” John Hancock building features a beacon on top that changes color depending on the weather forecast. Many older Bostonians can still recite the rhyme that cracks the code: “Steady blue, clear view / Flashing blue, clouds due / Steady red, rain ahead / Flashing red, snow instead.” During summer and fall, flashing red means the Red Sox game is cancelled (though snow isn’t out of the question at that time of year either).