Los Nevados National Park
Los Nevados is a national park centered around some snow covered volcanic peaks; Nevado Del Ruiz, Nevado del Tolima and more. The park is run by a "concession" - Concesion Nevados - Which actually is the travel agency Aviatur. Although not ruining the park entirely, it does feel more like an alpine resort than a national park. In practice this means that the park is privatised and that the goal of the park is to shuttle as many people as possible up the roads and down again.
Flora and fauna
Very interesting flora, layered in different heights.
Reasonably cold. Expect frosty mornings (0 - -10 C) year around. In the wet season, expect clouds continuously, in the "dry season" expect clouds 10 AM to 3 PM, and clearer conditions before and after.
The usual way to get in is from Manizales. From there you have several options: Go on a tour and jump off (120'000 COP incl. entrance and breakfast), Taxi (300'000 COP) take a bus to the intersection and hike/hitchhike up. The last option is the best one if you have the time, as you would gradually acclimatise to the altitude, not pay excessively, and avoid the extremely commercial feel of the Concesion.
Entrance fee is 53,000 COP for foreigners, 33,000 COP for Colombians and 6,000 COP for students and kids between 5 and 12.