Zoos are weird places: miniature other worlds designed for non-human occupants.
For the architect, they're also astonishing artefacts, little cities of architectural fantasy of amazing diversity; some of the greatest architects in the world from Lutyens to Norman Foster have built animal houses.
But how do we, and have we, designed for animals? What kind of architecture results? What are these human interpretations of what we think animals want? And how has our understanding of the natural world changed the kinds of environments we make for them?
Tom Dyckhoff tells a story about where we are and where we're going - what will zoos look like in 50 years time? Will they even exist?
Producer: Martin Williams.