- MADHATNEWS! The US city of Portland in Oregon is home to a unique weekly cycling event known as zoobombing. It attracts an eclectic crowd of cycling enthusiasts who like nothing more than hurtling down a steep hill at high speed, on souped up children's bikes, late at night.br br Watch more crazy Zoobombing videos at br br Some of the bikes are left chained up in a pile in the city centre, which has itself become a local landmark. The ride, often repeated several times in an evening, starts with a journey on Portland's light rail system then a hike to the top of a hill, near the city's zoo.