New Delhi, May 22 -- The oldest bridge in Paris has begun to vanish this week, as the artist JR - who is known as the "French Banksy" - began inflating a giant "cave" over the Pont Neuf.

The monumental, rocky illusion is swallowing the 17th-century landmark, which has carried Parisians across the Seine for more than 400 years. By Thursday, it looked as if a prehistoric cliff had risen in the heart of the city.

The inflation process, which was carried out overnight - after being delayed by bad weather - is the most dramatic stage yet of a project more than a year in the making.

One of the most ambitious public artworks Paris has seen in decades, which has been funded by the sale of JR's work and a handful of corporate partners, does not...