An eight-floor modern glass building, housing a shopping centre, will open next to the historic St Paul's Cathedral later.
The £500m One New Change will have 60 stores and restaurants spread over three floors and office space.
Developers said the building was "designed in sympathy with its rich architectural surroundings".
In 2005 Prince Charles had written a letter to the developers expressing his concerns about the project.
The building next to the Christopher Wren-designed 17th Century cathedral, has more than 6,000 floor-to-ceiling glass panes and will accommodate 3,000 workers in 330,000 sq ft (30,658 sqm) of office space.
Robert Noel of developers Land Securities said: "One New Change has been designed in sympathy with its rich architectural surroundings.
"The City mall will bring high-street brands, independent shops and unique concept restaurants to the City, to complement its world-class financial services and the area's extensive repertoire of museums, art galleries and breath-taking architecture."
In 2009, it emerged that the prince wrote a private letter to the chief executive of developer Land Securities about the architect - a French modernist Jean Nouvel - they assigned to the project One New Change.
He had also expressed his concerns about a steel and glass complex next to a historic location. Prince Charles's aides said he was perfectly entitled to write the private letter in 2005.
Marks & Spencer chairman Sir Stuart Rose, will declare the premises open later.