For climbers , the Andes offer incredible variety - from volcanoes to shale summits, from the continent's loftiest giants to some of its fiercest technical walls. You do not have to be a technical expert to reach the summit of some of these and, though you must always take preparations seriously, you can often arrange your climb close to the date through local agencies - though it's best to bring as much high-quality gear with you as you can. The climbing season is fairly short - November to March in some places, though December to February is the best time. The best-known challenge is South America's highest peak, Aconcagua (6962m), accessed from the city of Mendoza. Not considered the most technical of challenges, this peak nevertheless merits top-level expedition status as the altitude and storms claim several victims a year, some of whom are experienced climbers. Permission to climb must be obtained in advance from the Subsecretaría de Turismo in Mendoza, in person or through a tour company, and climbing fees are high (as much as $120 in peak season). Only slightly less lofty are nearby Tupungato (6750m), just to the south; Mercedario (6770m) just to the north, near Barreal in San Juan Province; Cerro Bonete (6872m) and Pissis (6779m) on the provincial border between La Rioja and Catamarca further north; and Ojos del Salado, the highest active volcano in the world (6885m), a little further north into Catamarca. The last three can be climbed from Fiambalá, where you're required to register with the police; but Ojos is most normally climbed from the Chilean side of the border. The most famous volcano to climb is the elegant cone of Lanín (3776m), which can be ascended in two days via the relatively straightforward north eastern route. The two-day southern route involves tackling a heavily crevassed glacier and is for experienced climbers only. Parque Nacional Nahuel Huapi, near Bariloche, offers the peaks of the Cerro Catedral massif and Cerro Tronador (3554m). And southern Patagonia has been a highly prized climbing destination ever since the Italian Salesian missionary, Padre de Agostini, published his Andes Patagónicos in 1941. One testing summit is San Lorenzo (3706m), which, from the Argentinian side, can best be approached along the valley of the Río Oro, although the summit itself is usually climbed from just across the border in Chile. Further south still are the inspirational granite spires of the Fitz Roy massif and Cerro Torre , which have few equals on the planet in terms of sheer technical difficulty and the grandeur of the scenery. On all of these climbs, but especially those over 4000m, you must acclimatize thoroughly, and be fully aware of the dangers of puna , or altitude sickness .