ARCHITECTURE fanatic BRAD PITT has spent £50,000 building a bespoke run - for his children's gerbils.
The Hollywood heavyweight is fascinated by design and construction and personally oversaw every step of the project at his family's French estate.
It features a maze of tunnels, seesaws and platforms which makes the rodents the most pampered vermin on the planet.
In 2005 the Inglourious Basterds star had an informal apprenticeship with Frank Gehry - one of the world's top architects.
Brad helped design a development for the seafront in Hove, East Sussex, but it has not been built.
A source said: "Brad pores over architectural journals like other people pore over newspapers. He had so much fun putting the run together with his kids MADDOX, ZAHARA, SHILOH and PAX.
"It's incredibly complex and cost a lot but Brad's more than happy with any activity that can combine his two passions - his kids and architecture."