Pico Viejo is a subsidary peak of the main Teide volcano and although the name means 'old peak', it is in fact younger than the main summit. The origin of the eruption can clearly be seen on the upper slopes of Pico Viejo, this point is known as the Las Narices del Teide or 'the Nostrils of Teide. The route of the walk crosses the lava flow as it heads for Montaña del Cedro and there are stunning views of the lava fields and of the central volcano complex.
There are also excellent views across the caldera to Montaña Guajara, the second highest independent summit on the island. The walk eventually climbs onto the caldera rim for more superb views before reaching a small cave housing the Fuente del Cedro. This spring keeps the floor of the cave permanently under water and it's surprising to see water in such an arid landscape.
The walk continues now to a firewatch tower and the view changes to give sweeping views down the southwestern flanks of the island to the Guia de Isora region and also to the Teno Mountains around Masca in the west.
From the firewatch tower, a wide track is followed back to the lava fields before the route returns via the outward path. The walk takes around 3.5 hours overall and although it is not too difficult, the rewards are great with outstanding scenery throughout.