Uruguay occupies 176,215 square kilometers on the southeastern Atlantic coast of South America, bordered by Brazil to the north and northeast and Argentina to the west. The Río de la Plata forms the country's southwestern boundary, while the Atlantic Ocean creates 660 kilometers of eastern coastline. The Río Uruguay, approximately 1,838 kilometers in total length, forms the entire western border with Argentina from Salto in the north to where it meets the Río de la Plata near Nueva Palmira. This is the second-smallest independent nation in South America after Suriname. The territory sits entirely between latitudes 30° and 35° South and longitudes 53° and 58° West.
The terrain consists of gently rolling plains interrupted by low hill ranges. No point in Uruguay reaches 600 meters above sea level. Cerro Catedral, the highest point at 514 meters, stands in the Cuchilla Grande range in Maldonado Department near the town of Aiguá. The Cuchilla Grande extends from northeast to southwest through the country's interior, forming a watershed divide between rivers flowing west to the Río Uruguay and those flowing south to the Río de la Plata or east to the Atlantic. The Cuchilla de Haedo, another significant range, runs parallel through the northwest. These hill systems formed from ancient crystalline Precambrian rocks that once connected to similar formations in southern Brazil and parts of Africa before continental drift. The landscape lacks dramatic elevation changes—most of the country sits between 100 and 300 meters above sea level. Approximately 90% of Uruguay's surface consists of gentle undulations suitable for agriculture and livestock grazing. This topography results from millions of years of erosion that wore down what were once much higher mountain ranges.
The Río Negro bisects Uruguay from northeast to southwest, flowing approximately 750 kilometers from its source in Brazil to its confluence with the Río Uruguay near Mercedes. This river system drains the central portion of the country. Between 1945 and 1982, Uruguay constructed three major hydroelectric dams on the Río Negro: Rincón del Bonete (completed 1945), Baygorria (completed 1960), and Palmar (completed 1982). The Rincón del Bonete reservoir, also called Embalse Gabriel Terra, covers approximately 1,070 square kilometers, making it one of the largest artificial lakes in South America. The Río Uruguay itself generates hydroelectric power through binational projects with Argentina—the Salto Grande dam completed in 1979 produces approximately 1,890 megawatts shared equally between the two countries. These river systems provide approximately 95% of Uruguay's domestic electricity generation in years with normal precipitation.
The Río de la Plata estuary measures approximately 290 kilometers long and widens from 2 kilometers at its upstream end near Nueva Palmira to 220 kilometers at its mouth where it meets the Atlantic Ocean. Debate exists over whether to classify this as a river, an estuary, or a gulf—the International Hydrographic Organization classifies it as a river until the line connecting Punta del Este in Uruguay with Cabo San Antonio in Argentina. The water appears brown due to sediment carried by the Paraná and Uruguay rivers, which together drain approximately 3.1 million square kilometers of interior South America. Salinity remains low throughout most of the estuary, though it increases toward the Atlantic. The estuary contains fresh water species near Montevideo, transitioning to brackish and marine species toward Punta del Este. Montevideo sits on the estuary's northern shore where water depth in the port reaches approximately 10 meters in dredged channels. Tides in the Río de la Plata remain minimal, typically under one meter, but strong winds can raise or lower water levels by two to three meters within hours.
Uruguay's Atlantic coastline extends from the Río de la Plata mouth at Punta del Este northward to the Brazilian border at the Arroyo Chuy. This coast features sandy beaches interrupted by rocky headlands, coastal lagoons, and occasional low cliffs. Cabo Polonio, approximately 260 kilometers east of Montevideo in Rocha Department, forms a rocky peninsula jutting into the Atlantic. The cape sits within a protected area covering approximately 26,000 hectares established in 2009. Cabo Polonio lacks electrical grid connection and road access—visitors walk approximately 7 kilometers from the nearest parking area or take modified truck transport through coastal dunes. The lighthouse at Cabo Polonio, built in 1881, stands 26 meters tall and remains operational. Isla de Lobos sits approximately 8.5 kilometers offshore from Punta del Este. This island reserve hosts one of the largest South American sea lion colonies, with population estimates ranging from 200,000 to 400,000 individuals depending on season. The island covers approximately 41 hectares. The Uruguayan government declared it a protected area in 1992. Access requires special permission except for authorized tourist boats that circle the island without landing.
Coastal lagoons punctuate the Atlantic shoreline. Laguna de Rocha, approximately 72 square kilometers in area, sits behind a barrier beach that periodically opens and closes based on water levels and wave action. When closed, the lagoon fills with fresh water from surrounding streams. When the barrier opens naturally or through human intervention, salt water enters and the ecosystem shifts between fresh and brackish conditions. This lagoon received Ramsar Convention wetland designation in 2015. Laguna Garzón, smaller at approximately 17 square kilometers, lies north of José Ignacio. A circular bridge designed by architect Rafael Viñoly opened in 2015, replacing a ferry and creating a distinctive landmark visible in satellite images. The bridge measures 280 meters in circumference with a diameter of approximately 90 meters. Laguna de Castillos, the largest coastal lagoon at approximately 90 square kilometers, sits further north in Rocha Department. These lagoons provide critical habitat for migratory birds moving along the Atlantic flyway.
Laguna Merín forms part of Uruguay's northeastern border with Brazil. This lagoon measures approximately 3,750 square kilometers total, with roughly 35% lying within Uruguayan territory. The lagoon extends approximately 174 kilometers from north to south and reaches 56 kilometers at its widest point. Average depth measures 3 meters with maximum depths near 7 meters. Water flows from Laguna Merín through the Río San Gonçalo into Laguna dos Patos in Brazil, eventually reaching the Atlantic near Rio Grande. This lagoon ecosystem supports extensive wetlands. The Bañados del Este, a wetland complex associated with Laguna Merín and coastal lagoons, covers approximately 400,000 hectares and received Ramsar designation in 1984. These wetlands include permanently flooded areas, seasonally flooded grasslands, and palm savannas.
The Palmares de Castillos region in eastern Rocha Department contains thousands of yatay palms (*Butia yatay*), creating one of the southernmost palm groves in the Americas. These palms grow scattered across approximately 70,000 hectares of grassland. Individual trees reach 10 to 15 meters in height and can live over 200 years. The palm distribution relates to past climate conditions warmer than present. Botanists documented approximately 180,000 palm individuals in surveys conducted in the 1990s. The ecosystem faces pressure from livestock grazing that prevents palm regeneration when cattle consume seedlings. Several protected areas exist within the palmares zone, though much remains on private ranch land.
Quebrada de los Cuervos, located in Treinta y Tres Department approximately 60 kilometers from the city of Treinta y Tres, became Uruguay's first natural protected area in 1986 and was designated a national park in 2008. The quebrada is a steep valley approximately 1 kilometer long where the Arroyo Yerbal Chico has cut through sedimentary rock layers creating cliffs up to 100 meters high. The valley harbors subtropical forest vegetation distinct from surrounding grasslands. Tree species include *Sebastiania brasiliensis*, *Lithraea brasiliensis*, and *Matayba elaeagnoides*. The microclimate in the valley bottom remains more humid and sheltered than the surrounding landscape. Similar but smaller quebradas exist elsewhere in eastern Uruguay where streams have incised into escarpments. These valley systems provide habitat for forest species at the southern limit of their range.