Ruta Nacional (RN) 3 is Argentina’s other great North – South highway, stretching from Buenos Aires to Ushuaia, before ending its 3074-kilometer (1910 mi) journey in Parque Nacional Tierra del Fuego. It is the major commercial artery, connecting Patagonia and Tierra del Fuego with the nation’s capital.

After reaching Carmen de Patagones, the last town in Provincia de Buenos Aires and gateway into the Patagonia, Ruta 3 edges the Atlantic coast. Crossing the Negro River, the highway enters Río Negro Province's capital, Viedma, then turns west to San Antonio Oeste. Near this city, off the main carretera is Balneario Las Grutas. The next town of note is Sierra Grande, where a track goes to another local beach town, Playas Doradas. After passing into Chubut Province is foreigners’ most popular stop along Ruta 3, Puerto Madryn. This booming tourist town is famous for the southern right whales (Eubalaena australis) that visit every year between June and December and Área Natural Protegida Península Valdés. Ruta 3 has now entered the Welsh Heartland: Trelew with its renowned paleontological museum; Rawson, the provincial capital; Playa Unión, one of the best places to spot Commerson’s dolphins (Cephalorhynchus commersonii); Gaiman, famous for traditional Welsh teas; and Dolavon, a sleepy Welsh farming hamlet. On the coast south of Trelew is Área Natural Protegida Punta Tombo, the largest Magellanic Penguin colony on the continent.

The next major city on RN 3 is Comodoro Rivadavia, the petroleum heart of the nation. Midways between Trelew and Comodoro is the turn-off for RN 30 east to Camarones. The seaside village was the childhood home of President Juan Domingo Perón and is the access point for Reserva Natural Cabo Dos Bahías and the new Parque Marítimo Costero Patagonia Austral. West from Comodoro Rivadavia is Ruta Provincial (RP) to Sarmiento, with important paleontological sites of pertrified forests and dinosaurs.

After Comodoro Rivadavia, Ruta 3 enters Santa Cruz Province, with a fascinating history of failed Spanish settlements, explorations by Charles Darwin, extensive sheep estancias and the bloody 1920-21 workers strike. The highway passes through Caleta Olivia, a major transportation hub, and Fitz Roy before arriving at Jaramillo. Here RN 281 wends to Puerto Deseado. Near this port village is Reserva Natural Ría Deseada, the only place on the South American continent where Rockhopper Penguins (Eudyptes chrysocome) live. South of Jaramillo is RN 49, which cuts across the Patagonian steppe to Monumento Nacional Bosques Petrificados. Ruta 3 continues its southward journey, through Tres Cerros, to Puerto San Julián. One the sea front of this port is a life-size replica of one of Magellan’s ships. Great coastal hiking is also awaiting the visitor. Next is Piedra Buena, from where Puerto Santa Cruz and Parque Nacional Monte León, with a large sea lion colony (Otaria flavescens), can be reached. Then RN 3 heads into Río Gallegos, another major transportation hub with a museum for every day of the week and good birdwatching.

After this, Ruta Nacional 3 crosses the Magellan Strait to the Chilean part of Tierra del Fuego. At San Sebastián, the highway once more enters Argentine territory. Ruta 3 visits Río Grande, Tolhuín and Ushuaia before ending its sojourn on the shores of Bahía Lapataia in Parque Nacional Tierra del Fuego.

Lodging, food and auto services are good the entire length of Ruta Nacional 3. Some stretches of the highway are long, straight and boring. Road fatigue is danger. Take 10 minutes of rest for every two hours of driving. The Patagonian winds are legendary and will affect gas mileage. Keep fueled up. Beware of flying pebbles, which can cause significant damage. If renting a car, check the policy on cracked windshields. Slow down for guanaco and choique (rhea) wandering out onto the road. Although Ruta 3 is paved, winter snows and ice can make it dangerous to travel, Always check current road conditions at the local tourism office or the police before heading down the road between fall and spring. Tire chains may be necessary. Bus service operates year-round, though also in the cold months service may be affected. Hitching on RN 3 is much easier than on Ruta 40 (several couples have reported making Río Gallegos to Buenos Aires in five days).