There are several ways up Cerro San Cristobal to the Parque Metropolitano, but only one doesn't require undue exertion: the Funicular , or funicular railway, which starts near the popular Bellavista area and which stops at the Zoo halfway up.   (until the end of december at least though, it is under repair or maintenace, but there is a free bus ride in the meantime). As of Feruary 27 2013, funicular is still under renovation and free bus still operating.

It leads up to the viewing area of the park near the summit of Cerro San Cristobal and is a lot easier than riding or walking, although both these are optional extras. A return ticket costs about CLP$2300 (or U$4).

If you prefer to walk down then, unless you try some of the steep shortcuts, you'll follow the long and winding road for over an hour and end up a Metro ride away from your starting point. The walk is hard work in the heat, although you'll pass plenty of fit Santiagans running or cycling up.

Another refreshing option is to try a Mote con Huesillo (Mow Tay con wess ee yo) which is a sweet, ice cold concoction of rehyrdated dried peaches, wheat, and sugar... best to try rather than think too much about it, it's great. At the top of the hill, on the lookout, several shops sell all manner of tourist gear and one in the middle serves the best Mote con huesillo (600 pesos a big glassful, with peach and wheat, or 400 pesos just for the juice).

There is also the Enoteca restaurant but on a much fancier level. 

There are two public swimming pools in the park, the Tupahue and the smaller Antilén, which are open in summer.