Arecibo sits on Puerto Rico's north coast, where the Arecibo River meets a small Atlantic inlet roughly 40 miles west of San Juan. It is the largest municipality in the commonwealth by land area and the anchor of the Arecibo Metropolitan Statistical Area, which forms part of the broader San Juan–Bayamón combined region. The municipality is organized into 18 barrios, or administrative subdivisions, together with Arecibo Pueblo, the compact downtown district that serves as its civic and commercial center. The area's modern identity is shaped by two overlapping stories. One is its colonial and maritime past: Arecibo was among the earliest European settlements on the island, and its coastline still bears reminders of that era, including the Morillos (Arecibo) Lighthouse completed by the Spanish government in 1898, the last such light built before the Spanish–American War. The other is its scientific legacy. For more than half a century, the Arecibo Observatory and its 1,000-foot radio telescope, set into a natural sinkhole south of town, made the name Arecibo familiar to scientists worldwide; the telescope operated from 1963 until its collapse in 2020. Economically, Arecibo has long balanced manufacturing and pharmaceutical activity with agriculture in its inland barrios and commerce centered on the Pueblo. Its sheer geographic spread means daily life varies widely across the municipality, from dense urban blocks near the plaza to quiet rural roads in the karst hills. That variety — coastline, cave country, farmland, and a historic downtown — is what gives Arecibo its particular character, and it continues to draw residents who want a full-service city with direct access to both the Atlantic and the island's interior.