The architectural remnants of the age cannot be avoided. They endure–with their windowless façades, their human-repelling scale, their masses of dirty concrete and their self-conscious wish to shock. Worse things happened in the 20th century, but few were more puzzling than the way Americans let their landscape be ravaged by architects and planners, particularly in the years between World War II and the 1980s. … Josep Lluis Sert’s ghastly Holyoke Center still occupies the spot in Harvard Square where Massachusetts Avenue’s beautiful line of Victorian brick was ripped apart to make way for it in the 1960s. Gerhard Kallmann’s Boston City Hall still sits like a Stalinist mausoleum on an empty, windswept plaza, for which dozens of ancient city blocks were razed. You can work westward from there. …