The testicles of a famous bull mosaic in Milan, Italy are being restored to former glory after being worn away by tourists spinning and stomping on it, honouring a historic tradition.

A famous bull mosaic artwork in one of Milan’s grand arcades is getting a delicate restoration of its “sensitive parts” after being worn down by tourists honouring a peculiar tradition.

The legend goes that grinding your heel on the bull’s testicles and spinning in place three times guarantees good fortune and return to the city.

Thousands of twirling visitors and their grinding heels left a shallow cavity where the bull’s testes used to be. According to city authorities, the pink tiles that make up its testicles have been worn down, forming a small crater

The beige and blue mosaic of a prancing bull is part of the flooring in Milan’s historic 19th-century Galleria Vittorio Emanuele II arcade. It is representative of Turin, the first capital of Italy.

Artisan Gianluca Galli, a restorer, is working on the mosaic project. Galli, talking about the spinning ritual which was popular among Milanese even in the 19th-century, told AFP, "It's probably a charming gesture, but also quite damaging for a work of art."

Due to the popularity of the testicle ritual, the artwork has to be cared for frequently. The last restoration of the bull mosaic was in 2017. Unable to pirouette on the bull while it’s under repair, tourists reportedly perform a similar act on a neighbouring ‘she-wolf’ mosaic representing Rome.