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.

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.

Boston City Hall has been declared a local historic landmark for its iconic — if sometimes controversial — brutalist architecture, Mayor Michelle Wu announced Friday. The 1968 structure, sometimes referred to as one of the world’s ugliest buildings,