Rafting the Maipo River is very popular among Santiaguinos and foreigners alike. It is just incredible that this activity exists so close to a major metropolitan city. Although the season runs from September to April, the river really gets going from November to February, when rafters can expect to ride Class III and IV rapids. Two companies offer half-day rafting excursions: Cascada de las Animas (tel. 2/861-1303; www.cascadadelasanimas.cl) is based in the Cajón, and they arrange rafting trips from their tourism complex in San Alfonso, but it's best to reserve beforehand. Another highly respected, and much friendlier, outfitter is Altué Expediciones, in Santiago, Encomenderos 83 (tel. 2/232-1103; www.altue.com). They are based in Santiago and can arrange transportation for you to the Cajón de Maipo.
The same two companies above offer horseback riding in the Cajón de Maipo, either for the day or for multiday riding (with themes such as "Following Darwin's Footsteps"). I can't express enough how enjoyable a horseback ride in the Andes is: the sweeping views from high, the grassy meadows, galloping home . . . There is an indefinable magic about crossing the Andean peaks the way Butch Cassidy and the Sundance Kid did. Cascada de las Animas has tours through its own private chunk of the Andes, but verify that your guide is bilingual when booking as they like to send out old ranch hands who just lope quietly along with you. Horseback rides are suitable for families and even those with little experience.