Colonia del Sacramento sits on a peninsula jutting into the Río de la Plata, directly opposite Buenos Aires across some 50 kilometres of brown river water. A UNESCO World Heritage Site since 1995, its historic quarter — the Barrio Histórico — is one of the best-preserved colonial towns in South America, a layered palimpsest of Portuguese and Spanish occupation that stretches back to 1680.
The Portuguese founded the settlement to challenge Spanish dominance of the river trade, and the town changed hands repeatedly over the next century: Portuguese, Spanish, British, Portuguese again, Spanish again — more than once after lengthy sieges. This history has left the Barrio Histórico with an unusual character. The streets are narrow, cobbled with rounded river stones, and lined with low colonial houses painted in faded pastels; the ruined walls of old forts overlook the water; and the old lighthouse rises from the shell of a convent. Almost everything in the historic quarter is within easy walking distance of everything else.
The most visited street is the Calle de los Suspiros — "Street of Sighs" — a single block of cobblestones lined with restored colonial houses. It is unquestionably photogenic, though also very visited. More interesting, in many ways, are the quieter streets to the west, the ruins of the San Francisco convent, and the Plaza Mayor where several small museums huddle around a central square. The Basílica del Santísimo Sacramento faces one side of the plaza.
Colonia is an easy day trip from Buenos Aires — the ferry takes an hour — but it rewards an overnight or two. The town slows down pleasantly after the day-trippers leave, the restaurants improve notably in the evenings, and there is real pleasure in wandering the empty streets in the early morning before the boats arrive.