If you're looking for a break from the ubiquitous ribollita, stop in at this eatery, which may be the only Japanese restaurant in the world to be housed in a 15th-century Renaissance palazzo. High, vaulted arches frame the Kaiten sushi conveyor belt. It's Japanese food, cafeteria style: selections, priced according to the color of the plate, make their way around a bar, where diners pick whatever they find appealing. Those seeking a more substantial meal head to the second floor, where Japanese barbecue is prepared at your table. The minimalist basement provides a subtle but dramatic backdrop for a well-prepared cocktail.