Once, long ago, Venice was plagued by a gang of thieves who had in their employ a magician. Each night he would wander the city, scattering his spells into every alleyway and backstreet.
He charmed these streets to draw in passersby, irresistibly drawn in by the siren song of cracked plaster and overflowing drains. These curious travellers would be met by the thieves, their throats and purses opened by quick razors and gold rings cut from their fingers, their corpses discarded in some quiet canal.
Today, the thieves are gone. The carabinieri hunted them down years ago, the last one a senile old man bedecked in gold and jewellery from his glory days, but insensible to the world. However, the spells still remain in place, despite numerous expensive efforts by the Venetian government to exorcise them. (Indeed, two mayors have lost their jobs after very public failures to counteract the magic.)
So, when people wander through the city today, they find their feet rotating to point down battered, silent alleys, their legs conspiring to propel them to their doom. Travellers are compelled to wander the backstreets of Venice forever, waiting for an end that will not come.