ApproachTo get to the trailhead, start in Manizales. There is no public transport to the trailhead, so you'll have to check several tour companies for a trip. The road heads east and up the mountain to El Secreta, where you turn south on a dirt road to the trailhead. We paid $10 a person for five people, which included a tour of the Ruiz area and a visit to the hot springs, and a lunch. Park entry was an additional $10 and there was a small fee to bathe in the hot springs in El Secreta.
Route DescriptionTo climb the mountain simply have the driver from the tour company drop you off at the base of Ruiz, which is located at the old Ruiz Refugio. No directions are needed for the climb, simply climb the steep sandy/snow slope to the crater rim in about 2 or 2.5 kms. The elevation gain is only 531 meters (1742 feet), so this is one of the easiest places in the world to reach this high of an elevation.
The route was formerly a large glacier, but the eruption and warming has melted much the glacier. The route still is covered with snow and ice for much of the distance, so an ice axe is handy, but there are only a few very tiny crevasses. Crampons are always required to reach the true summit at the present time.
If you don't have crampons and a rope, you will have to stop at 5146 meters.
It is likely that the mountain will slowly build larger glaciers again and that the route will eventually change.
Enjoy the spectacular views from one of the deadliest mountains in the world. Also, make sure to acclimatize somewhere, as the trailhead is at 4790 meters (15,715 feet)!
Note: The peak is oftten closed due to eruption danger and other reasons. In that case you will have to settle for climbing Olleta Crater, just west of Ruiz.
2008 UpdateUpdate from Federico1:
As of 2008, access to the summit has become more controlled.
You must pay an entrance fee and have an obligatory guide. Tourist can climb to the “sightseeing point” at 5146 meters. In order to get to the true summit, you must have a special permit that must be obtained two weeks in advance and cost $100 (with a guide).