Fountain is considered a landmark work of modernism
A 77-year-old Frenchman has spent a night in custody in Paris after attacking a plain porcelain urinal considered to be a major artwork.
The urinal - called Fountain - was slightly chipped after the man hit it with a hammer on Wednesday.
The piece by French-US artist Marcel Duchamp was on display at the Pompidou Centre in Paris.
Police said the man had urinated on the same piece at an exhibition in Nimes, southern France, in 1993.
The work, a replica of the 1917 original , is on display as part of a wider Dada exhibition, is believed to be worth some 3m euros (£2m).
Police said the man claimed the hammer attack was a work of performance art that Marcel Duchamp himself would have appreciated.