The 'Gringo trail' (not to be confused with the Inca trail) is what everyone calls the most frequently travelled route through and around South America. Gringo derives either from 'green go home' (in the days when the US Army used to wear green uniforms), or from greigo, the Spanish for Greek. Despite assurances in the guidebooks that the term is widely used in friendly reference to anyone with a pale complexion, this is definitely not a complimentary form of address. Just watch how a blond Argentine reacts to being called a gringo. The trail begins in whichever gateway happens to be the cheapest to fly into from Europe or the USA. Let's start in the north, in Colombia. The coast here boasts beautiful golden beaches, clear water and crystal streams cascading down from the 5,800 m summits of the Sierra Nevada. To the south is the big industrial port of Barranquilla, followed by Cartagena, an impressively fortified town dating from 1533 which for nearly 300 years served as a conduit for gold and treasures looted by the Spanish from their colonies. Continuing further south through hot swampland, then inland up the attractive forested slopes of the Cordillera Occidental, the traveller emerges on to the high plateau where Bogotá is situated, at an altitude of 2,620 m. Here the magnificent Gold Museum has over 10,000 examples of pre-Colombian artefacts. An hour away are the salt mines of Zipaquira, in the bowels of which is an astonishing 23 metre-high cathedral carved by the miners.

South of Bogotá are the Tequendama Falls, the splendid valley of the Magdalena river and, high up in the Magdalena Gorge, the village of San Agustín. Here, hundreds of primitive stone statues representing gods of a little-known ancient Indian culture guard the entrances to tombs. The road then loops back over high moorland to Popayan, a fine city with monasteries and cloisters in the Spanish style. The tortured landscape near here resembles violently crumpled bedclothes; recent reports suggest that it is not safe to travel on public or private transport in this region, so check with local sources before you go. Now the road crosses into Ecuador. Just north of Quito, the Equator - La Mitad del Mundo - straddles the road a few hundred metres from the grand stone monument built to mark the meridian. Quito itself lies at an altitude of 2,700 m, ringed by peaks including the volcanoes of Pichincha. The city's fine colonial architecture boasts (according to the South American Handbook) no fewer than 86 churches, many of them gleaming with gold.

The Andes

Crossing the Andes, travellers pass from near-Arctic semi-tundra, through temperate forest and equatorial jungle and down to the hot total desert of the Peruvian coast, punctuated by oases of agricultural land where irrigation has distributed the melt- waters from the Andes over the littoral. Here, too, the ancient empires of the Chavin, Mochica, Nazca and Chimu people flourished. Ruined Chan-Chan, near Trujillo, was the Chimu capital; nearby Sechin has a large square temple, 3,500 years old, decorated with carvings of victorious leaders and dismembered foes.

A popular detour from here turns inland at the fishing port of Chimbote to head for the Callejon de Huaylas. The route passes through the spectacular Can-on del Pato, where the road is literally drilled through the rock wall of the canyon, with 'windows' looking down to the roaring maelstrom of the Santa river below.

The Callejon de Huaylas valley runs along the foot of the Cordillera Blanca; here a 1970 earthquake buried the town of Yungay under an avalanche of mud. The towns of Caraz and Huaraz make good centres for walking and trekking in the Cordillera, and the road south across the mountains offers spectacular views of the snow-capped Cordillera Blanca.

The coast near Lima is picturesque and rich in fish and birdlife, owing to the effects of the Humboldt Current. Lima itself has both shanty towns (barrios) and affluent suburbs, parks and fine beaches. Well worth seeing are the National Museum of Anthropology and Archaeology and the Gold Museum at Monterrico on the outskirts of town.

South from Lima

From Lima there are two routes south. One branches into the mountains (the pass reaches 4,800 m), passing through the zinc-smelting town of La Oroya and on to Huancayo. The railway line along this route has recently been reopened - check departures at Des Ampararados station, behind the presidential palace in Lima. The road continues through Ayacucho and Abancay to Cusco. The alternative route follows the fast coast road through the desert, past the wine centre of Ica to Nazca, with its vast network of ancient and mysterious lines, and on to Arequipa. There are several short-cuts - from Pisco or Nazca, for example - or you can take the train in a great circle from Arequipa to Cuzco.

One thing is certain: any route across the Peruvian Andes is tortuous, time- consuming, and stunningly spectacular. Although the route from Lima to Cuzco looks relatively short on the map, for instance, it actually represents about 50 hours of continuous travelling overland. Cuzco, sitting in a sheltered hollow at 3,500 m, was the capital of the Inca Empire. Inca stonework forms the foundations of many of the later Spanish buildings, and the ancient city layout survives to this day.

Overlooking Cuzco's red roofs is the ruined fortress of Sacsahuaman. Within a couple of hours' drive are the Inca ruins of Pisac and Ollantaytambo. Accessible by train only, down the valley of the Urubamba (called the Vilcanota further upstream), is the 'Lost City of the Incas', Machu Picchu. The magnificent ruins, nearly 500 m above the river, were invaded and overgrown by the jungle until their discovery in 1911. Several legends add to the mystery of the lost city. According to one, the Incas fled after the sacking of Cusco to this city, whose existence was unknown to the Spanish invaders. According to other legends, the Incas themselves erased all mention of the city from their oral histories as retribution for some (now forever censored) local uprising long before Pizarro and his men set foot in Peru.

From Cuzco, the road crosses the watershed of the Andes to the dry and dusty Altiplano, a high, treeless plateau stretching across much of the Bolivian upland. Here lies Lake Titicaca, at 3,810 m the world's highest navigable lake, blazing a deep blue through the effects of strong ultra-violet rays. On its rocky islands the Uru-Aymara Indians continue their traditional lifestyle. Across the border in Bolivia are the ruins of the ancient temples of Tiahuanaco, with the famous carved Gate of the Sun. La Paz sits in a valley just below the rim of the Altiplano, the city centre lying at approximately 3,500 m.

La Paz and beyond

From La Paz, there are three possible routes, depending on the size of the circuit you intend to make:

1. Eastwards through the relatively low-lying city of Cochabamba to Santa Cruz, then on by rail to Corumba on the Brazilian border, from where you can head for Sâo Paulo or the Iguaçu Falls. The road from Santa Cruz to Corumba and all routes from Bolivia to Paraguay are suitable for four-wheel-drive vehicles only.

The road south of Puerto Montt goes only as far as Coyhaique. The most usual point for crossing the border south of Santiago is near Osorno, which brings you to Bariloche, now a fashionable ski resort in Argentina. This route may not be passable in winter (June to October). The road from Santiago to Mendoza via Uspallata is kept open all year round; it uses the railway tunnel and does not pass the famous statue of Christ of the Andes. Travel south from Bariloche takes you over frequently unmade roads in the foothills of the Andes, through the beautiful Argentine lake district to Viedma and El Calafate. Here the lakes are fed by melt- waters from the Patagonian ice cap, and their creeks are sometimes blocked by tongues of glacial ice. The scenery around Lago Argentino is some of the most spectacular to be found anywhere in the world. Roads here are passable at most times of year, though from June to October four-wheel drive vehicles are advisable.

Alternatively, you can combine the Pan-American highway with local ferries, travelling via the island of Chiloe and the Chonchi-to-Chaiten ferry. You can also travel east out of Puerto Montt, using the local balsa or ferries to cross the numerous rivers and fjords on the way to Chaiten. The road continues down to Cochrane, but ferry services stop from June to October. Bear in mind that heavy rains periodically cause landslides which put an end to all hope of travel.

The south

It is possible to reach South America's southernmost tip, Tierra del Fuego, by ferry from near Rio Gallegos, or from Punta Arenas across the border in Chile. From June to October it is often impossible to cross the mountains by road in order to reach the small town of Ushuaia on Tierra del Fuego's south coast, but there are regular flights throughout the year from nearby Gallegos and Rio Grande.

It is well worth making an excursion from Punta Arenas in Chile to Puerto Natales and the famous Torres del Paine National Park: a must for mountaineers, and an unforgettable experience for anyone who thinks that those etchings by early explorers always made mountains look improbably precipitous.

The fast and straight east coast road takes you north again through temperate scrubland, via Comodoro Rivadavia and Puerto Madryn, with its Welsh-speaking colony, to Bahia Blanca and Buenos Aires. This cosmopolitan city of nearly ten million inhabitants lies on the estuary of the Rio Plata, a few hours by ferry from Montevideo in Uruguay.

Most travellers tend to bypass the rolling cattle-grazed plains of Uruguay in favour of the roads northwards, either through Santa Fé and Resistencia to Asunci-n, or direct to Iguaçu via Posadas and the Misiones province. Ferries are now almost extinct, but new bridges (Ponte President Tancredo Neves between Argentina and Brazil, and the Friendship Bridge between Brazil and Paraguay) make the journey quicker, if less interesting. There are also three bridging points across the Parana River between Buenos Aires and Asunci-n: the first is at Zarate; the second is the tunnel from Santa Fé to Rosario; and the third is the bridge between Resistencia and Corrientes.

There is a good fast road from Asunci-n to Foz do Iguaçu, where a bridge straddles the frontier. Another bridge links Foz do Iguaçu (Pôrto Meira) in Brazil with Puerto Iguazu (or Iguassu) in Argentina, making it possible to visit these spectacular falls from both sides of the river.

The plantations of Brazil

The dense forest that once spread across Brazil from Iguaçu to Rio and beyond is gradually giving way to coffee and soya bean plantations. A particularly special stretch of forest road follows the Serra do Mar coastal range from Curitiba to São Paulo, its east- and west-bound carriageways frequently separated by several kilometres of jungle-clad mountain.

From São Paulo there are two routes: one through Santos and Angra dos Reis along a beautiful coast road; the other a fast motorway following the ridge of the mountains via the steel town of Volta Redonda. Rio is a focal point from which routes divide once more:

From Brasilia, several routes lead up to the Amazon basin, the fastest and easiest heading direct to Belém via Anapolis. This road offers a short cut at Estreito, along the Transamaz-nica Highway to Altamira and Santarém.

Alternatively, you can follow the newer road west to Cuiabá and then take the Transamaz-nica north to Santarém. From both Belém and Santarém there are river steamers to Manaus, though car ferries are few and far between. A more practical route for travellers with their own vehicles heads west to Cuiabá and Pôrta Velho, then north along the new road via Humairá to Careiro on the south bank of the Amazon, opposite Manaus. From here there are three ferries daily to Manaus.

In the heady days when Brazil enjoyed the world monopoly on rubber production, Manaus built a splendid (and recently restored) opera house for the best mezzo- sopranos in the world, and the rubber barons lit their cigars with 1000 millreis notes. Most of that glitter has now faded, though edifices built from stone imported from Britain can still be seen.

From Manaus, river boats ply the Rio Negro and the Rio Branco, tributaries of the Amazon, providing a break from overlanding and a convenient, if primitive, way of visiting remote villages. North of Manaus, the authorities have 'subdued' unrest among the local Indians, and the route is now passable in safety.

Angel Falls

The road between Boa Vista and the gold mining town of El Dorado in Venezuela winds through spectacularly beautiful country, passing the sheer-sided 'lost world' of Mount Roraima at the point where Venezuela, Brazil and Guyana meet. Trips can be taken to the world's highest waterfall, Angel Falls (979 m), from El Dorado or from Puerto Ordaz (now part of the new city of Ciudad Guayana).

After crossing the Orinoco, you soon reach Caracas, having completed almost a full circle of the continent. If you still want to see more, you can take a route eastwards that is definitely not on the Gringo trail. Border disputes make it impossible to cross the frontier from Venezuela to Guyana.

From Boa Vista in Brazil, however, a road of sorts leads to the frontier and a fordable river into Lethem. In the dry season, it is possible to drive all the way to Georgetown, and on along the coast to the Corentyne river. Getting across the river and into Nieuw Nickerie in Surinam will cause problems for those with their own vehicles, though there is an infrequent ferry. It is in fact possible to drive all the way to Cayenne in French Guiana, though the road is little more than a sand track in places and a number of rivers have to be crossed by ferry.

Saint Laurent lies just over the river from Surinam, in French Guiana, and the remnants of both this penal colony and the better-known one on the Isles de Salut (including hard-to-reach Devil's Island) are beginning to prove something of a tourist attraction.

At Cayenne the road comes to an end, though it is possible to fly either direct to Belém at the mouth of the Amazon or to Saint Georges just across the river from the Brazilian river port of Oiapoque, from where a road runs all the way to Macapa. From here there are ferries to Belém, which puts you back on the route southwards to Rio, either along the north-eastern coast or south to Brasilia. In fact, you could just keep circling and recircling the continent in ever decreasing circles, clockwise and anti-clockwise. It's a very dizzying part of the world in every respect.