BMW's GS series is one of the world's milestone motorcycles and has been in production for over 25 years. It pioneered the 'adventure sport' category big bikes that are capable of travelling off-road and, in many ways, it's the Range Rover of motorcycling. It's now more popular than ever, thanks in part to the massive publicity surrounding the film Long Way Round featuring Ewan McGregor and Charley Boorman.