Mendoza is a desert that somebody decided to turn into a garden. Under 250 mm of rain a year falls on the city, yet the streets are lined with trees and cut by irrigation channels called acequias, fed with water diverted from the river. The city you see is young. On 20 March 1861 an earthquake flattened the old town and killed around 4,000 people, and the survivors rebuilt about a kilometer to the southwest with wide avenues and a ring of plazas, so that people would have open ground to run to next time. The city today is that plan, aged into shade.
The same irrigation made the wine. Malbec came from France in the 1860s, and Mendoza now grows the biggest share of it in the country, on slopes between roughly 800 and 1,500 meters. Five days is the right length because Mendoza is really a city and four outings. The city is easy and slow, the wine districts need a full day each if you want to taste properly, the Andes road to Aconcagua is a long day on its own, and a river-rafting and hot-spring day rounds it off. Do it in less and you either skip the mountains or taste wine in a hurry, which defeats the point.
The plan: day one is the city and its park, day two Luján de Cuyo and Maipú, day three the Uco Valley, day four Ruta 7 up to Aconcagua, and day five rafting at Potrerillos, the hot springs at Cacheuta and sunset from the Cerro de la Gloria. Start on a Tuesday, so that day two falls on a Wednesday: the Casa de Fader museum is open Wednesday to Sunday, the Maipú bike shop is closed on Sundays, the 1884 restaurant is closed on Mondays, Catena Zapata is reported to take visits Tuesday to Saturday and many wineries only take weekday bookings. Mendoza is also the starting point for much of Argentina. For the capital, see 5 Days in Buenos Aires.