Teide is the highest point in Spain, a 3,715-metre volcano on Tenerife that stands on a plain of black lava inside a caldera sixteen kilometres wide. The caldera, Las Cañadas, is the collapsed shell of an older and taller mountain. Its floor of red and ochre lava, cinder cones and wind-cut towers is so like Mars that space agencies drive their rovers over it before launch. Climbing Teide takes you out of the weather. A cable car lifts you from 2,356 metres to 3,555 in about eight minutes, breaking through the trade-wind cloud into sunlight above a white sea. Only a couple of hundred people a day are let onto the last stretch to the crater rim, so the top is nearly empty, and up there the ground steams faintly with sulphur under your boots. The neighbouring islands stand out of the cloud below you.
Down on the caldera floor the Roques de García stand in a row, cut by wind; the slenderest, Roque Cinchado, leans with the cone behind it in the most photographed view on Tenerife. In late spring the grey floor flushes red with tajinaste, which grows on this island and no other. It spends two years or more as a rosette of silver leaves, throws up one three-metre spike of red flowers, sets seed and dies. To the Guanche, who had Tenerife before the Spanish, the mountain was Echeyde, hell, with a demon shut inside it; they read the pale plug of rock capping the summit as the seal. Late in the day the caldera walls deepen to copper and the mountain lays its own shadow across the plain as a triangle. Then the sky takes over: more than three hundred clear nights a year, and the Milky Way standing over the caldera. The observatory on the ridge is up here for the same reason the cable car is — above that cloud, the air hardly ever closes.