Sardine is a lovely restaurant. The ceiling is high, like in a converted warehouse. The building overlooks the water. The menu is simple and refined to the point of being printed on a place mat - but don't be fooled. They have truly delicious food. Service is formal and agreeable.
Word to the wise: this restaurant is populated largely by academics at UW-Madison. If you want to bump into a professor or a scientist, this is not a bad place to get lucky. Watch out though - it's hard for them to argue about plasma physics when they're drunk on the good stuff, and Sardine serves plenty of it.
Best things on the menu? OYSTERS! They always have a selection of raw oysters on the half shell. I get that and champagne. Then I usually move on to the salmon with lentils and buerre blanc.
Probably my top pick in Madison. If you're female, dress mousy but make sure your hair is ultra-shiny. If male, put on a bow tie and a tweed jacket with leather elbow patches, fasten your cuff links, groom your goatee and shine your shoes. Pretend you have an English accent. Ok, NOW you're ready for Sardine.