The Schönbrunn Zoo in Vienna is widely regarded as one of the best in the world and is certainly the oldest and the most beautiful. Established in 1752 by the Habsburg Imperial Family, the zoo has a circular layout that spirals outwards from an elegant Baroque pavilion and a reputation for successful conservation and breeding of some of the world’s most endangered species, including Siberian tigers, rhinos and giant pandas. In 1904, a glass-and-steel hothouse was built in Art Nouveau style to protect the vast collection of rare tropical plants owned by Emperor Franz Joseph I; over a century later this hothouse has been renovated and transformed into a show-home for cacti and other water-retaining succulents from arid regions across the world. Desert animals and birds such as lizards and humming birds roam free and there are several enclosures containing snakes and bizarre desert mole rats, which resemble a cross between a tiny walrus and a hairless rabbit. Equally eccentric is the Welwitschia tree from the Namibian desert, which has long, droopy fronds and grows in an untidy heap along the ground; it can live for up to 1,500 years.