436 under the bridge

Description: Steffi and Lola take a walk in the near city forest, as they have a funny idea. They blow up one ghost face printed balloon and place it the trees. Maybe some passers will get scared. Some minutes later, the girls arrive under a highway bridge. Steffi always wanted to hear a balloon pop under such an huge bridge. So, both girls blow up balloons and let them pop with a never before heard bang.