Cerro San Cristóbal is a nearly the tallest hill in Santiago and home to it's largest public park; Parque Metropolitano. It has a height of about 300 meters (just under 1,000ft) above downtown Santiago, although nary a bump compared to the towering Andes in the background. Its original indigenous name was Tupahue. It was named by the Spanish conquistadors for St Christopher.
At it's highest point, there is a church with an amphitheater, and a 22 meter statue of the Blessed Virgin Mary that was donated by France in the 1920s. Pope John Paul II gave mass here in 1987. This is the best spot to view Santiago although the city's smog can put a damper on this. One of the best times is in the winter after a good rain and if you're lucky the clouds would have also cleared giving you the full beauty of the surrounding mountains.
On one side of the hill you can find the Metropolitan Zoo, a sort of half-way house of animals from around the world that should probably be someone other than in the smog of a south american city. There's also a Japanese-style garden and two municipal pools, Tupahue and Antilén, that are open for the summer season. Although the pools are a little pricey (about US$10) for south america, they are well kept. If you had to choose between the two, I would recommend Antilén as it's usually less crowded although a little out of the way. There are also many places throughout the hill that offer a great place for a picnic, weather permitting.
To get up the hill the park has 2 cheap options at the two entrances to the park.
Entrance #1 -
Take the Metro (or walk if you like) to station Baquedano. Walk north, crossing the river and until the end of Pio Nono street. This is where you will find the Funicular.
Entrance #2 -
Take the Metro to station Pedro de Valdivia. Getting out of the metro, walk east (toward the Andes mountains) just a bit until you come to Pedro de Valdivia street and then walk north. After a long block you’ll arrive to the river. Cross the bridge and continue several more blocks until you reach the end of the street. This is where you will find the Teleferico.
If you're short on cash or just like the exercise, you can opt for the roads starting on both sides and joining about half way up. From these roads you can bicycle or walk up the hill. From the Pedro de Valdivia entrance there's a small snack stand that has bicycle rentals. For walking though, you're best off starting from the Pio Nono entrance. Just a hundred or so meters from the start of the road there's a trail that can get you to the top in about 25 minutes.