Just 8km from the center of Pasto, Volcán Galeras (4267m), one of Colombia's most active volcanoes, continues to rumble and threaten. The upper part of the volcano is preserved as a national park, Santuario de Flora y Fauna Volcán Galeras, while its lower slopes are a patchwork of farms and bright-green pastureland.
Much of the park has long been closed to the public due to the risk of eruption, however, the area around Telpis is open to visitors. Here you will find the Laguna de Telpis, a mystical lake surrounded by páramo (high-mountain plains) at more than 3000m, reachable via a 6km-long trail.
To visit from Pasto, take a taxi to Yacuanquer (COP$4000) from the parking lot in front of the bus terminal, then continue in either a moto-taxi or colectivo (both cost COP$2500) to the village of San Felipe. In San Felipe you will need to contract a guide (around COP$30,000 per group of up to 10 people) for the three-hour hike to the mirador (lookout).
You'll need to arrive at the park before noon or you won't be let in. Good shoes and cold-weather gear are essential for this hike.