See a gap, jump it.

See a rail, vault over it.

See a wall, climb it.

These are the instincts of traceurs, adoptees of a French-inspired sport called parkour that is part obstacle course, part pushing the limits of urban architectural functionality and all adrenaline-pumping excitement.

Parkour developed 16 years ago in the suburbs of Paris when sneaker-clad teenagers began navigating public spaces as skateboarders might, but without the skateboards. (The name comes from ''parcours,'' French for circuit or course.) From Paris it made its way to England, and then as far as Finland and Singapore. Using moves from gymnastics and martial arts and a name, traceur, that evokes tracer bullets and radioactive isotopes, parkourists tear through urban landscapes using obstacles like walls, ledges and stairs as springboards and catapults — rarely with any safety equipment. It might look effortless, but it takes months just to master the proper way of rolling out of a jump.

He runs up walls, leaps on to narrow ledges hundreds of feet above the street and jumps from rooftop to rooftop. TV viewers this week have been spellbound by a new BBC1 promo showing real-life Spiderman, 28-year-old French athlete David Belle, performing a series of stomach-churning stunts over the rooftops of a busy city. …

The rooftop surfing, however, is part of a new form of urban martial arts currently taking France by storm. Called Le Parkour — the obstacle course — it is a mixture of acrobatics and daredevil antics developed by martial arts expert Belle. Obviously, concentration and grace of movement are crucial.