1857 Lighthouse (Faro), Convento de San Francisco Ruins & Plaza Mayor 25 de Mayo Guide

Opening out at the centre of the San Gabriel peninsula, Plaza Mayor 25 de Mayo was laid out in 1680 by Portuguese founder Dom Manuel Lobo as the Largo da Matriz (military parade ground). Today, shaded by towering sycamore (plane) trees, palms, and pink-flowered palos borrachos, this broad cobbled square links the city's colonial museums with its most striking architectural juxtaposition: a nineteenth-century white brick lighthouse growing directly out of the stone walls of a seventeenth-century Franciscan convent.

1. Ruinas del Convento de San Francisco Javier (1683 to 1704)

At the south-western corner of Plaza Mayor stand the thick, moss-covered rubble-stone walls of the Convento de San Francisco Javier, one of the oldest colonial structures in Uruguay. Built between 1683 and 1694 by Franciscan friars using local granite boulders held together with mud and lime mortar, the convent and its chapel were gutted by a catastrophic fire in 1704 during the War of the Spanish Succession and never roofed again.

2. Climbing the 1857 Faro de Colonia del Sacramento

To prevent shipwrecks on the rocky shoals surrounding Isla San Gabriel and Isla Farallón, construction began in 1855 on a cylindrical white masonry lighthouse wedged right into the corner of the ruined convent nave. Lit on 24 January 1857, the Faro de Colonia del Sacramento rises 26 metres above its base (34 metres above the level of the Río de la Plata). Visitors can climb the narrow interior spiral stone staircase (followed by a short vertical iron ladder at the top; check the ticket booth at the base for current daytime hours) out onto the circular lantern balcony for an unforgettable 360-degree panorama across the red-tiled roofs of the Barrio Histórico, the offshore islands, and, on clear afternoons, the distant skyline of Buenos Aires across the river.

3. Exploring the Four Sides of Plaza Mayor 25 de Mayo

After descending from the lighthouse, walk a slow loop around the perimeter of Plaza Mayor: along the northern and western sides stand the 18th-century stone houses of the Museo Portugués, Casa de Nacarello, and Museo Municipal Dr. Bautista Rebuffo; along the eastern side sit open-air courtyard cafés and the 18th-century foundations of the Paseo de San Gabriel.