Cafes with scenic settings are a rarity in Tokyo, so this lovely spot looking out over the rowboats on the moat is worth a stop if you're in the neighborhood. Lunches start at around Y1,000, and for an extra Y1,000 you can add on a salad bar and (soft) drinks bar.
After 5pm it's a proper restaurant, with surprisingly good upper-level Italian fare, including a nice assortment of small appetizers and lots of good-value wines. Budget around Y6000-9000 for dinner. There's also a separate, more informal section of the cafe next to the boat docks; they're open for coffee a little later in the evening.