Marmalade has been the standard-bearer of upmarket dining in Old San Juan for almost two decades — chef Peter Schintler's tasting-menu restaurant on Calle Fortaleza, decorated like a curated nineteenth-century parlour with deep banquettes and chandeliers. Expect five or six courses built from local seafood, root vegetables, and Puerto Rican proteins reworked in a contemporary register: white bean soup is a long-standing signature.
Tasting menus only; pairings are well-judged and add roughly half again to the bill. Book a few days ahead, especially for weekends. The dress code is smart-casual; the small bar at the front is a fine place for a single cocktail if you cannot get a table.