In each of the two cities Linz and Budapest a foot bridge made of wooden planks are installed. If someone steps on a plank in one of the cities, an impulse released from the body weight is immediately sent to the other bridge. So a pulse can be felt in the other city, as the parallel plank lifts itself around 1 cm which releases a pounding noise. One can feel realistically the footsteps of strangers in a foreign city.

(via Interactive Architecture)