The council issued a tender for private companies to install and run the wheel on a three-month trial this summer, after which it might be moved.
The project has also been approved by the local cultural heritage superintendency as a way to attract more tourists.
"We can't keep getting by with the Leaning Tower alone," heritage councillor Salvatore Sanzo said.
"We must think of something different and a giant wheel could make the difference."
Heritage and conservation body Italia Nostra said the project should be regarded "with caution", as a modern wheel would be out of place in the medieval and Renaissance city.
Italia Nostra Tuscany chief Mariarita Signorini compared the project to the London Eye, observing that it was part of a major city that "has a very modern soul with skyscrapers and other large buildings".
With ANSA
