Global fast-food chain McDonald's is suing the Italian city of Florence for €18m (£16m, $19.8m) after it was stopped from opening a new restaurant on a historic plaza. The US chain planned on opening a branch on the Piazza del Duomo in the centre of the city.

The plaza boasts the stunning Cattedrale di Santa Maria del Fiore, once the largest building in medieval Europe, which began construction in 1296, as well as the Baptistery of Saint John and Giotto's Campanile. Much of the centre of Florence is a UNESCO world heritage site.

In June, the chain's plans were rejected by Florence's mayor Dario Nardella. This decision was then upheld in July by a panel charged with preserving the city's ancient roots. McDonald's had adapted their proposals to fit in with city guidelines, and have now launched a bid for damages.

The world's largest fast-food chain is claiming that they have been discriminated against, and want to recoup the €18m they believe they will lose over the next 18 years, according to local newspaper Firenze Today.

They say that they have "(operated) respectfully towards the local policies, even accepting to introduce typical local products in our offer, as requested from the local commerce regulation".

"We completely agree that the cultural and artistic heritage and the Italian historical town centres have to be protected and guaranteed, as well as the traditions and the historical small shops, but we cannot accept discriminatory regulations that damage the freedom of private initiative without being advantageous to anyone," McDonald's told the BBC in a statement.

Nardella says that the city was not prejudiced in rejecting the bid to open the restaurant on the piazza, which already has bars, ice-cream vendors and restaurants nearby. He told the city council earlier this year: "McDonald's has the right to submit an application, because this is permitted under the law, but we also have the right to say no."

McDonald's serves around 550 million Big Macs around the world and is worth an estimated $37bn. The company opened its first restaurant in Italy in 1986, near the Spanish Steps in Rome. In October it was reported that cardinals serving in the Vatican City had been angered by plans to open a McDonald's in a piazza next to Saint Peter's Square.