Nondescript from the outside, but far prettier within – thanks largely to its famous collection of antique clocks (don't be late, now!) – the Decameron is a stalwart paladar (privately owned restaurant) that was always good, still is good and probably always will be good. The food is Cuban with international inflections. People rave about the savory tuna tart, risotto and swordfish.
On top of that there's a decent wine selection and powerful cocktails. The kitchen is sympathetic to vegetarians.