Mount Teide rises 3,715 metres above the Atlantic, its caldera spanning seventeen kilometres and enclosing a lunar terrain of pumice fields, obsidian flows, and weathered basalt towers that inspired Alexander von Humboldt's pioneering work on altitude ecology in 1799. The stratovolcano last erupted in 1909, and today Teide National Park preserves the largest concentration of endemic flora in Macaronesia, including the red bugloss that flowers only above 2,500 metres and the Teide violet found nowhere else on Earth. UNESCO inscribed the site in 2007, citing its geological testimony to oceanic island evolution and its role as a natural laboratory for studying volcanic processes on isolated landmasses. West of the caldera, the Teno massif unfolds as the island's oldest exposed geology, a shield volcano that began building five million years ago and now presents sheer barranco walls sculpted by millennia of flash floods. Masca village clings to a ridgeline at 650 metres, its twenty stone houses accessible only by a zigzag road carved in 1991; before that date, residents relied on mule trails and cultivated terraces of almonds and potatoes on slopes that drop 600 metres to the sea. The ravine below became a smugglers' route in the eighteenth century, and twentieth-century isolation preserved vernacular architecture and dry-stone terrace systems that are now protected under regional heritage law. Garachico, once Tenerife's principal port, was buried under lava during the 1706 eruption of Volcán Trevejo, which destroyed the harbor and forced the island's maritime economy north to Puerto de la Cruz. The molten basalt cooled into a jagged shoreline of tide pools—El Caletón—where seawater fills natural basins at every high tide, creating a network of volcanic swimming enclosures framed by columnar jointing and pillow lava formations. The town rebuilt itself around the Castillo de San Miguel, a sixteenth-century fortress that survived the flow, and today Garachico's historic quarter holds twenty structures listed on Spain's Bien de Interés Cultural register, including the convent of San Francisco and the neoclassical parish church that replaced the original buried chapel. The Teide Masca Garachico Grand Tour connects these three geological and cultural landmarks in a single transect across West Tenerife, ascending through five climate zones from coastal desert to alpine scrub, crossing the island's drainage divide, and descending through laurel forest and banana plantations. The circuit passes the Dragon Tree of Icod de los Vinos, a specimen estimated at 800 years old and standing seventeen metres tall, and traverses the Orotava Valley, where colonial-era trade routes linked highland pine forests with harbor warehouses. Modern volcanic tourism infrastructure includes the Teide cable car, installed in 1971 and renovated in 1999, which lifts visitors to La Rambleta station at 3,555 metres in eight minutes, leaving a final 160-metre scramble to the summit crater that requires advance permit from the national park authority.