The official said the couple had rented the 16th century Belvedere Fort for 300,000 euros ($411,100) for the occasion, which will be presided over by a Protestant pastor.
However, as the castle is not an authorised site for weddings, there was some question about whether the event will be an officially recognised marriage ceremony or a celebration with some looser status.
Asked how he was feeling as the day approached, West told the local La Nazione daily: "Quite emotional. But very happy. I'm a romantic: I gave Kim a wall of flowers for Mother's Day. Family is everything for me, it's the antidote to the stresses of fame. Family and creativity relax me."
The couple will be accompanied by their daughter North, who West said was "conceived here, among the masterpieces of the Renaissance".
"It was our first honeymoon. It's one of the most beautiful cities in the world, for me, it's the most beautiful in Europe."
Representatives for Kardashian and West did not immediately respond to requests for comment.