Historically, Rome is the answer to this question.
But, other cities have also taken the moniker over the years.
What does Sheffield have in common with Rome and Amman? All three are built on seven hills.
Amman, Jordan
Amman is built on seven hills, or jabals, each of which more or less defines a neighborhood.
http://www.kinghussein.gov.jo/tourism1.html
Like Rome, Edinburgh is built on seven hills. But unlike Rome, in Edinburgh these hills are the remains of a series of extinct volcanoes.
http://www.s-h-systems.co.uk/tourism/edinburgh/orientation.html
Lisbon was rebuilt after a major 18th-century earthquake levelled many parts of it. It has also survived a shrinking empire, dictatorship and revolution. Today it is a relaxed, easy-to-see city which, like Rome, is built on seven hills. worldfacts.us/Portugal-Lisbon.htm
http://www.smh.com.au/articles/2003/11/04/1067708176587.html
Nevada City is built on Seven Hills
http://www.rootsweb.com/~cancgs/seven_hills_of_nevada_city.htm
Kampala, Uganda
In praise of Uganda's new capital, the colonialists described Kampala to London as "a very beautiful, legendary city built on seven hills like ancient Rome." Although it now spreads over more than 20 hills, it is still sometimes referred to as the city of seven hills. The legendary seven hills are Mengo, Lubaga, Namirembe, Old Kampala, Kibuli, Nakasero and Makerere.