When I visited Portland in Oregon recently I was introduced to the crazy world of Zoobombing. Simply put, a bunch of free-spirited bike enthusiasts meet every Sunday evening, to hurtle down a steep hillside on kids bicycles. They take the monorail up, and bike down. And they do it several times in to the early hours of Sunday morning.
The next day they go back to their jobs in the corporate world, local charity, coffee shop or the unemployment line. It is dangerous, takes place on public roads and is not recommended for children. But the local police are cool with it and there are rarely any accidents.
I would not do it. I value my limbs too much. But hats off to this dedicated crowd of thrill-seekers, their hospitality and bravado.
Video at BBC News