The Palacio de Cristal ("Crystal Palace") is a glass and metal structure located in Madrid's Buen Retiro Park. It was built in 1887 to exhibit flora and fauna from the Philippines. The architect was Ricardo Velázquez Bosco.
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The structure was designed in a way that would allow it to be re-erected on another site (as happened to the equivalent building in London). However, the building has remained on the original site, next to a lake, and has been restored to its original appearance. It is no longer used as a greenhouse, and is currently used for art exhibits..
http://en.wikipedia.org/wiki/Palacio_de_Cristal