Tenerife, 910m2, like all the Canary Islands, is a volcanic mountain thrust upwards from the seabed. In fact they say that the ocean floor is as deep as the mountain is high. The highest mountain, El Teide, is indeed the highest mountain in Spain at 3718m above sea level. This appears all the greater as it actually starts at sea level unlike most mountain ranges. It is not the only mountain, but just a part of the ancient crater that comprises the centre of the island. It then stretches away eastwards into a ridge, the Anaga that runs nearly the full length of the island and divides it into two slopes. The national park of El Teide covers a large part of this central crater and is about 17 kilometres long. Small roads criss cross this whole area, as do walking tracks, which are also cycleable only outside the boundaries of the national park.

As the climate differs from the North to the South, so does the flora. The North part of the island is wetter and therefore is greener and more forested than the South. There is a band of forest between about 1000 and 1800m. This is mainly composed of endemic Canary Island Pines a more robust slower growing pine than the Mediterranean variety. Although it is quite often cloudy on the North Side of the island of Tenerife it does not actually rain a lot. There is a phenomenon locally known as horizontal rain, which refers to the band of cloud that, that clings to the forest at that altitude, generally till around 3.00pm. This is where the island gets its water from, millennia of transpiration by these forests.

Above the forest line the countryside gets progressively more and more barren with endemic cacti adding to the more common prickly pear and agave and many other plants adapted to these harsh conditions. Tenerife has 58 endemic plants, including a very ancient tree called The Dragon Tree, the oldest of which is 1000 years old. Being a volcano with intermittent lava flows the formations of twisted and broken rock are quite incredible the newer flows completely barren with progressively greater plant life growing on the older flows. The variety of colours and types of rock is also staggering within the national park; there are in fact 12 different types of lava including obsidian.

The South Side owing to its dryer air is much more barren yet still displays the wonderful shapes and vistas unique to the volcano. In fact a lot of Tenerife's appeal is due to the fact that it is volcanic, high twisted mountains, different coloured lava flows with varying amounts of vegetation, canyons caused by the solidifying lava, waddis or dry river beds cut by the water rushing off the mountain side during the rare rain storms, amazing vistas in every direction from the mountains and along the south side varying colour sands on the beaches. On the South Side, there is the notorious black sand, though Tenerife does have some golden sand beaches as well.