Paris's world-famous skyline has a new shape. Rising up in the midst of the Eiffel Tower, Montmartre and Montparnasse is a white monster where the giant dome of the Pantheon is usually seen.

About 20 years since the spectacular wrapping of Berlin’s Reichtag by the artist couple Christo and Jeanne-Claude, a young Frenchman has wrapped the upper section of France’s most important historical building.

JR, as the 31-year-old artist calls himself, has installed a collage of thousands of black-and-white portrait photographs of important French figures on both the white-wrapped dome as well as inside the temple.

It’s not just the artistic project that’s wrapping the monument, but also a protective covering as part of a major restoration effort.

The more than two-centuries-old Pantheon is having problems because of its size. Most worryingly, the stone arches that serve to hold up the massive building’s 82-metre-tall dome are in danger.

Iron fittings in and around the arches are starting to rust from faulty insulation. As they rust, the bars are expanding and eating into the stonework, splitting the stones and threatening the stability of the arches.

The Pantheon, in the city’s Latin Quarter, was originally a church but now functions as a secular mausoleum containing the remnants of famous French citizens.

To prevent the hall of glory of such luminaries of French history as Victor Hugo, Emile Zola, Voltaire and Jean-Jacques Rousseau becoming a ruin, the first stage of renovation will undertaken on the dome, its top point, and the tambour, or circular wall, beneath the cupola.

Scaffolding weighing 315 tonnes has been erected to carry out the work – a difficult challenge as the scaffolding must also support a 96-metre-tall construction crane reaching to the top of the monumental building.

Paris Pantheon

The crane must be kept steady enough in the wind so that it doesn’t damage the architecture.

Daniele Dal is the woman at the Centre of National Monuments in charge of co-ordinating the restoration work on the Pantheon. She says the project is nothing short of spectacular.

“It’s not every day that such a scaffolding is erected. It is a complex restoration because this is all about architecture that is very special,” she says.

“Today, not even with the help of computers could we build another monument like the Pantheon.”

She says the dome consists not of one, but of three cupolas fitted inside each other, something not visible to the naked eye. Each individual building block must be cleaned or replaced.

Just the dome by itself will see 10,500sqm of stone being cleaned. There will also be any amount of work that cannot yet be calculated.

“It was only after we set up the construction scaffolding that we could get a picture of the real extent of the damage,” Dal says.

“All our studies and calculations we had previously done from down below.”

For example, it turns out the lantern that forms the top point of the Pantheon cannot simply be cleaned as planned, but must be built completely anew.

The dome of the Pantheon will be kept wrapped in white during the restoration work.

Meanwhile JR will make the huge edifice into a work of modern art with his photo installation.

If things go according to plan with the total restoration cost of 100 million euros ($A149.99 million), the Pantheon should be completely restored by 2022.

By Klara Froehlich