Northwest of Punta Arenas and Puerto Natales, the Torres del Paine National Park is located on a section of the Patagonian steepe and is the most popular park in Chile.
The Paine Circuit is a rugged loop around the Paine Massif which consists of four granite spires. Get ready for massive glaciers and dramatic waterfalls. Hike the Paine Circuit counter-clockwise starting from Laguna Armaga on the eastside. Its a 52 mile route that typically requires 10 days to circumnavigate. This orange-blazed route is best travelled counterclockwise. Keep in mind that solo hiking is prohibited. The route can be quite windy -- March is by far the best time of year to attempt it.
There are independently operated refugios and campsites along the routes.
To reach Torres del Paine National Park, plan to use inter-country airline, LAN Airlines, to fly from Santiago to Punta Arenas. Rent a car from Turismo Southland (011-56-61-241-143). Then drive 155 miles north to Puerto Natales. Then another 90 miles northwest to the park. Note, there may be bus service available from Punta Arenas to Puerto Natales.
Overall, Paine Circuit Loop is the 2nd most popular hiking trail of all 4 hikes in Chile.