The 340-acre Botanical Garden contains more than 5,000 species of tropical and subtropical plants and trees, including 900 varieties of palms (some more than a century old) and more than 140 species of birds. The shady garden, created in 1808 by the Portuguese king João VI during his exile in Brazil, offers respite from Rio's sticky heat. In 1842 the garden gained its most impressive adornment, the Avenue of the Royal Palms, a 720-meter (800-yard) double row of 134 soaring royal palms. Elsewhere, the Casa dos Pilões, an old gunpowder factory, has been restored and displays objects pertaining to the nobility and their slaves. Also on the grounds are a museum dedicated to enviromental concerns, a library, two small cafés, and a gift shop.