In 1954, leaders selected a partnership of three of Toronto's largest architectural firms: Marani and Morris, Mathers and Haldenby, and Shore and Moffat, to create a design.

Presented in November 1955, their design proposed a conservative, symmetrical limestone-clad building in the Modernist style facing a landscaped square.

Unlike the design that would ultimately be built, it retained the stone Beaux-Arts Registry Office on the western part of the site and also included a landscaped public space in front of it.

The scheme was panned by leading architects, including Frank Lloyd Wright (who called it a "sterilization" and "a cliché already dated") and Walter Gropius (who deemed it a "very poor pseudo-modern design unworthy of the city of Toronto"),[6] and all classes of the University of Toronto Faculty of Architecture co-authored a letter condemning the proposal and calling for an international competition.

Phillips assembled a five-person panel of judges from some of the world's greatest architecture experts with Eric Arthur serving as advisor.

[7] One of the two dissenting judges was William Graham Holford, who was skeptical that the design could be built within the $18 million budget set by the city.

He complained that not enough credit was given to his design collaborators, Heikki Castren, Bengt Lundsten, and Seppo Valjus, and asked that all names be listed as the architects.

The time capsule for City Hall was placed in a large ceremony on November 7, 1962 and Governor General Georges Vanier officially opened the new structure September 13, 1965.

The south side was vacant at the time of the City Hall opening but was eventually occupied by a new hotel, connected by a bridge over Queen Street to the square.

The opening ceremony was attended by 14,000 dignitaries, including Lester B. Pearson, the prime minister of Canada, and John Robarts, the premier of Ontario.

[citation needed] City Hall was designated as a property of historical and architectural significance under the Ontario Heritage Act in 1991.

The outer surfaces of the curve are covered with concrete bearing a rib pattern that provides strength and prevents collapse of the fabric as a result of the expansion of the exterior surfaces, and the tearing apart of the fabric as a result of differences in air pressure on the two sides of each wing-like tower during the high winds characteristic of the Great Lakes.

The design for the public space in front of the new city hall, Nathan Phillips Square, was part of the competition.

The square's reflecting pool and concrete arches, fountain, and overhead walkways were thus also part of Revell's submission.

It has since seen several monuments, sculptures, and other works of public art added, and was renovated, but it continues to complement the city hall with its original Modernist design elements.