Overview: Sir David Attenborough tells the stories of the world's best animal architects. There are house-proud bower birds, who only find a mate if they decorate their homes perfectly. There are hornets, who build electric central-heating systems, and the star-nosed mole whose house is so well designed that his favourite meal of worms literally drop in for dinner. From larders to nurseries and from high-rises to subway systems, Attenborough shows that the animal architects have designed it way before we humans.