Old San Juan.

Old San Juan is the historic, blue-cobbled heart of Puerto Rico’s capital. Established by the Spanish in 1521, this compact, walled peninsula was built as a military stronghold, a heritage still defined by its two massive colonial fortresses: Castillo San Felipe del Morro, which guards the harbor, and Castillo San Cristóbal, built to defend against land attacks. Between these towering landmarks lies an intimate, highly walkable grid of pastel-painted masonry buildings, breezy plazas, and historic sites like the 16th-century San Juan Cathedral and the governor's residence, La Fortaleza. What makes the district distinct is how effortlessly its five centuries of history blend into the modern day, with active cafés, shops, and restaurants tucked directly into the ancient stone fabric.