Tenerife, an 18th-century explorer's paradise

The Canary Islands, Spain's outermost region, once acted as a very important laboratory. There they tested how crops would cope on the mainland after being sent from the Americas.

The conditions found on the islands, as well as the attraction of Mount Teide, are what made Prussian naturalist and explorer Alexander von Humboldt keen to make a stop in Tenerife on the way to Central and South America in the late 18th century.

His journey was not like the one that the rich English explorers undertook. On his stop, Humboldt took advantage of this opportunity to explore Tenerife and make an inventory of the island which sits in the shadow of Mount Teide, Spain's highest peak.

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He walked, observed, and gathered material and new ideas. He stayed for six days, visiting Santa Cruz, La Laguna, Puerto de la Cruz and Orotava Valley. He also climbed Mount Teide.

The German scientist docked in the harbour of Santa Cruz on 19 June 1799. He disembarked from the Pizarro, a corvette lent to him by the Spanish Crown, along with fellow explorer, Aimé Bonpland, and the tools and measuring devices that he always had at his side.

In his unusual collection of instruments there was a theodolite, a tool used to measure angles on horizontal and vertical planes; a barometer to measure air pressure; a thermometer; a stopwatch; and a cyanometer, a device for measuring the blueness of the sky. That was not all, however.

He also carried a pair of binoculars, a sextant to measure the angle of any celestial body in relation to the horizon, and a book in which he recorded every single detail that captured his attention: native species such as the Canary dragon tree, lichens, ferns, bushes, flowers that lived at high altitudes, the variation in the climate, among many other questions and observations.

At that time, Santa Cruz was not the capital of the island, or even considered an important city. It was a commercial port where fishermen and poor people lived. From that 'sauna', Humboldt and his fellow companion travelled 15 kilometres to La Laguna, Tenerife's cooler and unfortified capital, located 550 metres above sea level. Its historical centre is well-planned, with wide streets and four-storey volcanic stone buildings with balconies.

After La Laguna, the pair travelled to Puerto de La Orotava which today is known as Puerto de la Cruz.

There they searched for locals to accompany them, and mules to help carry their equipment as they wanted to climb Mount Teide the next day. The ascent started on the black sand of Muelle beach in Puerto de la Cruz, just over 30 kilometres from Teide. Because of the versatility of this island, tropical plants and snow are never that far away from one another.

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Mount Teide is a volcanic pyramid, hidden in parts by clouds, a weather phenomenon known as the donkey's belly. The origins og the volcano are found at the bottom of the ocean 3,000 metres deep, and it rises to 3,718 metres above sea level at its highest point.

Before reaching the summit, Humboldt crossed what is known as Malpaís, a land devoid of vegetation and covered by fragments of lava. He reached La Rambleta, the edge of the first crater at an altitude of 3,550 metres.

Nine centuries ago, Mount Teide finished here. It grew a bit more after a series of eruptions which took place in the Middle Ages. The eruption created a new peak as the molten lava cooled and hardened. Today, when weather conditions are good, hikers can alight the cable car which covers the final stretch of the climb, a barren cone where only white broom grows.

At the summit, Humboldt, who was almost more interested in gaining knowledge than breathing, measured everything he possibly could until dawn. He then descended and left Tenerife. He continued his journey, visiting new places.

This intruder among scientists, as Humboldt described himself, stored unlimited knowledge of geography, astronomy, physics, zoology, ethnography, climatology, oceanography, cartography, geology, botanics and volcanology. An all-round rebel, thirsty for knowledge.