The Age of Enlightenment lives on in these formal gardens next to the Museo del Prado at the southwest corner of the Parque del Retiro. Carlos III, the so-called mayor-king, had Juan de Villanueva (architect of the Prado and the Paseos) design the gardens as a collection of temperate zone plants from around the world. The king himself opened the gardens in 1781. Through their history they have had their ups and downs—they fell into years of abandonment after the War of Independence in 1808—but today the meticulously maintained gardens contain more than 6,000 species of plants and trees. Nine self-guided visits are available, including tours focusing on ornamental, medicinal, and edible plants.