Throughout history men have always created personal spaces where they retreat to be among friends. Lately, these places, called "man caves", have become a boom industry, with often more than $50,000 (£31,772) being spent on furnishing a single "cave".

Jeff Wilser, co-author of The Man Cave Book, talks to the BBC's Franz Strasser about the forces behind these hideaways, why men are so protective of them, and why the variety of such caves is so immense.

"It's basically about finding what your one passion is, what your hobby is, and building a space that does that passion justice," says Mr Wilser.

Music courtesy of Stephen Clark.