Skateboarding
There's probably no city in USA or Europe where there are absolutely no skateboarders riding along the streets, on ramps or elsewhere. This sport has developed into a whole subculture with millions of its devotees around the world.
The first skates were invented in the US back in 1950-1960 when surfers decided to cut roller skates in two and attach their wheels to a surfing board. At first this invention was used for training surfers during bad weather when there was no possibility to surf in the sea. Surfers performed simple tricks that were necessary for successful surfing on the water like balancing or bypassing different obstacles. Later on first patents were acquired and skateboarding developed as a separate sport. People from the Surfer magazine decided to publish a new magazine devoted exclusively to skateboards. With time new materials and components were invented like polyurethane wheels, wider suspensions, new materials for the board itself like slippery plastic on the lower side of the board used for sliding on ramps etc. In 1975 skateboarding began its expansion all around the world, although in many aspects it was still like surfing. Anyway, in 1980 it was established as a separate subculture activity that distinguished teenagers from other people.
Like other extreme sports skateboarding has several subtypes today. It can be both a simple means of transportation and a way to do various stunning tricks like riding on hands, riding on only two wheels ("wheelie" or "manual"), jumping over an obstacle or flipping the board under one's feet.