Teide

Teide, the National Parque of Tenerife is absolutely amazing. The whole scenery seems like you are on the moon! It takes a bit of time to reach the top of the volcano and when you get there the air is so thin that you can hardly breathe, but it worths the effort!
It is an Unesco World Heritage Site.

Mount Teide or, in Spanish, Pico del Teide (Teide Peak), is the highest elevation in Spain and the islands of the Atlantic (it is the third largest volcano in the world from its base, after Mauna Loa and Mauna Kea located in Hawaii). It is an active volcano which last erupted in 1909 from the El Chinyero vent on the Santiago (northwestern) rift and is located on Tenerife, Canary Islands.
The volcano and its surroundings comprise the Teide National Park (Parque Nacional del Teide in Spanish). The park has an area of 18900 hectares and was named a World Heritage Site by UNESCO on June 29, 2007. Since the end of 2007, it has also been one of the Twelve Treasures of Spain. Midway up the mountain are the telescopes of the Observatorio del Teide. Territorially it belongs, for the most part, to the municipality of La Orotava, including also Icod de los Vinos, Los Realejos, Guía de Isora and ten more.
Teide is the most visited National Park in the Canary Islands and Spain, with a total of 2.8 million visitors, according to the Instituto Canario de Estadística (ISTAC). According to data for 2004, with its 3.5 million visitors annually, this volcanic landscape receives a large number of international visitors, second only to Mount Fuji in Japan. In 2010, Teide became the most visited national park in Europe and second worldwide. Teide is the most famous natural landmark in Tenerife and the Canary Islands.
Teide is a stratovolcano. At 3718 m above sea level, and approximately 7500 m above the floor of the Atlantic Ocean, it is the highest mountain in Spain and the highest point in the Atlantic Ocean. (Note: The actual summit stands 3 metres (10 ft) higher than the triangulation station, and associated bench mark, which has an altitude of 3,715 m (12,188 ft)). The island of Tenerife itself is the third largest volcanic ocean island on Earth by volume. Teide is also the third highest volcano on a volcanic ocean island. It is also unstable and possibly in a more advanced stage of deformation and failure than the much publicised Cumbre Vieja. The United Nations Committee for Disaster Mitigation designated Teide as a Decade Volcano, because of its history of destructive eruptions and its proximity to several large towns, of which the closest are Garachico, Icod de los Vinos and Puerto de la Cruz.
Teide together with its neighbour Pico Viejo and Montaña Blanca form the Central Volcanic Complex. [wikipedia]