When completed in 1986, Rialto Towers was the tallest office building in the Southern Hemisphere and was the first building to surpass the 200 meter threshold in Melbourne. The surrounding Rialto district was named in reference to the Venetian gothic architecture found on many of the 19th century buildings developed during the Melbourne gold rush. When the Rialto Towers was first planned in 1981, many of these older buildings from that period had already been demolished, leading to public outcry and the partial preservation of the remaining structures. The main footprint of the Rialto Towers is set into the middle and southern end of the block, preserving the scale of the historic streetscape along Collins Street. The building then rises from a podium base as two interlinked reinforced concrete towers, reaching 43 floors and 63 floors respectively.

The building rests upon 76 reinforced concrete caissons reaching up to 1.8 meters in diameter and 40 meters in below grade. The building’s concrete structure is composed of central service cores in each tower, with floor slabs spanning the distance between the core walls and the perimeter columns, proving for maximum flexibility with interior layouts. As the building approached 30 years in age, a new podium structure was designed and constructed around the base of the Rialto Towers and including a new interior atrium providing a new sheltered public space between the Collins Street sidewalks and the elevator lobbies of the office towers.