A boat cruise along the River Seine is one of most popular ways to see Paris, but angry locals are worried that a new installation may spoil the experience.
Bright-red, fully exposed, urinals have been placed across the city to reduce peeing on the streets.
But the eco-friendly devices, which are filled with straw and designed to be odourless, have left many unconvinced.
Furious residents are calling for the urinals to be removed and are planning to submit a petition.
One particular urinal, which has been placed near Notre Dame cathedral and overlooks passing tourist boats, has been singled out for criticism.
"There's no need to put something so immodest and ugly in such an historic spot," Paola Pellizzari, who owns a nearby art dealership, told Reuters news agency.
"It's beside the most beautiful townhouse... the Hotel de Lauzun," she said, adding that she was worried the urinal "incites exhibitionism".
"It's horrible," another resident said. "We're told we have to accept this but this is absolutely unacceptable. Can't people behave?"
But the local mayor, Ariel Weil, says the urinals are needed.
"If we don't do anything, then men are just going to pee in the streets," he told Reuters. "If it is really bothering people, we will find another location."
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Some argue that the "uritrottoir" - a combination of the French words for urinal and pavement - is discriminatory.
"Uritrottoirs for men, great. But what about us women? Litter trays? Sexist ideas are not nice," one Twitter user said [in French].
"They have been installed on a sexist proposition: men cannot control themselves and so all of society has to adapt," feminist Gwendoline Coipeault told Reuters.
"No one needs to urinate in the street," she added.