The Spanish Crown fortified San Juan's seven-block colonial core beginning in 1521, constructing what would become the oldest European-settled city under United States jurisdiction. Fort San Felipe del Morro—El Morro to residents—anchored the northwestern promontory in 1539, its six-level sandstone bastions rising 145 feet above the Atlantic. The colonial grid that unfolded eastward employed a deliberate urban logic: narrow streets channeled trade winds through the settlement, cooling interiors during the Caribbean summer, while overhanging wooden balconies—known as balcones—shaded pedestrians from the equatorial sun. By the late 18th century, the district housed 300 residences painted in the pastel palette that remains today: ochre, cobalt, coral, mint. Old San Juan's designation as a UNESCO World Heritage Site in 1983 recognized not only its military architecture but its preservation of Spanish colonial urbanism. The district's 465 buildings predate 1898, the year Spain ceded Puerto Rico to the United States. Restoration efforts in the 1940s under Ricardo Alegría reversed decades of neglect, stabilizing structures along Calle del Cristo and Calle Fortaleza. The district now operates as a living heritage zone, with residential apartments occupying upper floors above street-level commerce. Evening foot traffic peaks between 5:00 and 7:30 p.m., when temperatures drop from the day's high and the westward sun casts long shadows across Plazuela de la Rogativa. Walking the historic quarter after 5:00 p.m. offers practical advantages beyond aesthetics. Midday temperatures in August regularly exceed 88°F with humidity above 75 percent; by 6:00 p.m., the heat index typically falls 8 to 10 degrees. The golden hour—photographers call it hora dorada—occurs 45 minutes before sunset, when oblique light saturates the ochre walls of Catedral de San Juan Bautista and gilds the limestone facings of La Fortaleza, the governor's residence since 1540. An Old San Juan sunset walking tour moves through Paseo de la Princesa, a palm-lined promenade constructed in 1853, then ascends to the fortifications where the Raíces Fountain and San Juan Gate frame views of San Juan Bay. The district's compactness—seven square blocks—permits a comprehensive circuit in 90 minutes, though most guided evening walks extend to two hours to accommodate photography stops and historical context at each plaza.