1. The walled city is a UNESCO world heritage site and justifiably so. It is one of those places that has, in an odd twist of fate, benefited from years of poverty. The historic fortifications and colonial architecture were never subjected to the whims of modernization and thus remain in much the same state as they were in 16th and 17th century.
It is still possible to walk along the walls and ramparts admiring, to one side, the Caribbean and to the other, the colorful historic town. When that gets old, one can visit museums dedicated to the gold or emerald trade, or less romantically, to the practices of the Inquisition. Or if museums are not to your liking, it is possible to simply stroll through the charming little lanes, knowing that in a town this small, the probability of getting lost (even for the directionally challenged, such as myself) is slim.