Boston City Hall, known for its brutalist architecture, is now an official historical landmark despite once being named the fourth ugliest building in the world.

Boston City Hall has its admirers. And its detractors. But it’s an undeniable landmark of the city. And now it’s in writing.

To envision its new city hall, Boston held a competition in the 1960s and eventually selected the submission from architectural firm Kallmann, McKinnell, & Knowles. The design, then and now, was hailed by fellow architects as a classic example of the brutalist style.