classiest
Height of sophistication
Classiest is the superlative form of classy, describing someone or something that exhibits the highest degree of elegance, sophistication, or style within a given group.
That was the classiest restaurant I've ever been to.
The word carries connotations of taste and refinement, though it's often used with a touch of irony or informality that distinguishes it from more formal synonyms like most elegant or most refined.