Estufa Fría (cold greenhouse) of Parque Juan Carlos I

Parque Juan Carlos I lies in the Barajas district of north-east Madrid, close to the city's trade-fair grounds and served by the Feria de Madrid metro station. Its cold greenhouse, the Estufa Fría, was designed by the architects José Luis Esteban Penelas and Emilio Esteras Martín. BCP Ingenieros, which handled the structural engineering together with J. A. Torroja, dates the project to 1994 and the works to 1994-1997, and notes that the building reused a structure previously put up for the park's Plaza Central.

The City of Madrid gives 1996 as the construction date. The local blog Barajas BIC records an inauguration in May 2001, the year in which the building received a mention in the Community of Madrid's architecture and housing awards. It was then conceived as a climate-controlled teaching garden devoted to the Mediterranean climate and its flora.

In 2008, after a refurbishment that Barajas BIC says was completed in May, a botanical collection of 220 species and varieties of exotic plants was created there, forming a new educational trail in the park. The part designed as an exhibition hall fared less well: in 2015 Barajas BIC reported that it had stayed closed since 2001 and was deteriorating through disuse, and called on the city to find it a cultural use.

The Estufa Fría is a cold greenhouse: a semi-enclosed structure that creates an indoor microclimate by passive means, without consuming energy. It stands on a rectangular plan of 4,000 m² and rises to 12 m. Built of concrete and glass, it is partly sunk into the ground, and its roof and sides are made of concrete louvres.

The louvres are angled to block the high summer sun while letting in the low rays of winter. Together with the glass panels, the orientation and the partial burial, they provide natural climate control. The long axis of the building runs west to east, so most of the planted surfaces face north or south, and a slope partly shelters the north side.

The building originally had two parts: an exhibition area, intended as a museum of Mediterranean climate and flora, and a zone of shade houses (umbráculos) for the garden itself. Inside, a walkway leads up to the upper level, where the succulents are grouped. BCP Ingenieros describes the structure as the largest cold greenhouse in the world.

The botanical collection, created in 2008, brings together 220 exotic species and varieties in twelve areas. The best known is a Japanese garden with Zen-inspired features, pools, stone blocks, gravel and wood mulch, planted with bamboos, maples and flowering shrubs. A pond of aquatic plants includes papyrus.

Bamboos have an area of their own, with giant, yellow, black and weeping varieties, and further sections are given over to cycads and palms and to succulents. Another is reserved for acid-loving plants: camellias, rhododendrons, azaleas, hydrangeas and heathers. The route also takes in citrus trees, an evocation of riverside woodland, ferns in the dimmest part of the building and climbers covering walls and columns. Native plants of the Mediterranean climate are displayed outdoors.

The Estufa Fría stands at the centre of Parque Juan Carlos I, in the Barajas district, which is served by metro line 8 (Feria de Madrid station). Allow around an hour for the twelve areas, leaving time for the Japanese garden and the walkway.

The building closes whenever an orange weather warning is in force, as it is sensitive to wind. The visit combines easily with a walk through the park, along its sculpture trail, around the Olivar de la Reina Sofía olive grove and beside the Ría, the park's stretch of water. Little known even to many Madrid residents, the greenhouse makes for a quiet visit in any season.