The Belvedere Palace, one of the most emblematic buildings in the Vatican, dates back to 1484 and is undergoing a host of reforms to make it more green.

And one of the most radical is using milk as paint as it's much more "durable" say officials.

The milk is mixed with lime and natural pigments, in this case, the original cream colour, which was used in the sixteenth century and hand-applied on the walls with a century-old technique.

Vatican chief architect Vitale Zanchettin said: “We have no nostalgia for the past, but it (milk) is in fact more resistant".

The unusual move is a way of proving Pope Francis' commitment to the environment, and the Vatican also said it pays special attention to its plants, according to Italian publication, 20 Minutos.

The Vatican has unveiled a series of “green” measures that demonstrate Pope Francis’s desire to care for the environment. 

And the Vatican has been at the forefront of research on the use of essential oils to clean and protect the 570 statues and other marble works of art in their gardens. In this sense, plants are also under special care.

The symbolic building uses a permanent staff of 100 at the Vatican Museums which cleans and repairs art and old buildings for the six million tourists that visit the Vatican each year. 

It comes as residents of Rome are not entirely happy with the way city officials have entered into the Christms spirit.

Romans are up in arms over a Christmas tree that has been dubbed "Spelacchio". 

Roughly translated as mangy or baldy, the name given to the tree in the capital's Piazza Venezia has become a symbol of what many see as the eternal city's eternal decay.

One Rome resident said: “It's a disgrace. It hurts even to look at this Christmas tree. How can they have put it in Rome, a capital city like Rome.” 

Another added: “It is clearly dead and it represents a shameful spectacle for citizens and tourists.”

(Additional reporting by Maria Ortega.)