Perseus is the most established restaurant on Piazza Mino, and one of the few places in Fiesole with a serious local following rather than just a passing tourist trade. The menu is straightforwardly Tuscan — bistecca alla fiorentina, ribollita, pappardelle with wild boar, seasonal vegetables from the Mugello hills above. Nothing is precious or reinvented; the kitchen has been cooking this food for decades and knows what it's doing.
The outdoor tables on the piazza are the obvious draw in good weather, with a direct view across the square to the cathedral. Inside, the room is simple and warm. Reservations are a good idea at weekend lunches; on weekday evenings it's more relaxed. The wine list is focused on Chianti and Chianti Classico, as it should be at this altitude.