Most days, using London's Tube system is an ordeal. But during Tube Challenge 07 it is turned into a race course for especially intrepid types.
On 18 May, teams will square up and frantically visit every Tube station within Zone 1 (Central London) in as little time as possible. The current record to visit these 63 stations is a little under 3 hours.
More info about the Tube Challenge on Gadling.com or the official Tube Challenge website.
You should follow me on twitter here.