With initial investors such as Robin Williams and Robert De Niro, this sleek, cherrywood-lined restaurant, an offshoot of New York's famed Drew Nieporent restaurant empire, was destined to be a hot spot. It's not as trendy as it once was, but it draws a loyal clientele that appreciates a sophisticated after-work bar atmosphere, good food, and a big, smart wine list. The restaurant resides in a stately stone building from 1908. The downstairs dining room has the air of a men's club; the upstairs space is plainer. The menu, which stresses local, seasonal ingredients and European techniques, suits Rubicon's understated glamour.