Volunteers assemble a bridge made of cardboard and duct tape in Ostankino park in Moscow, Russia, on Aug. 1, 2019. A 18-meter-long flying bridge made of cardboard and duct tape was assembled and installed in Ostankino park of Moscow on Thursday. The bridge was lifted into the air with the help of three balloons filled with helium. (Photo by Maxim Chernavsky/Xinhua)

People look at a flying bridge made of cardboard and duct tape in Ostankino park in Moscow, Russia, on Aug. 1, 2019. A 18-meter-long flying bridge made of cardboard and duct tape was assembled and installed in Ostankino park of Moscow on Thursday. The bridge was lifted into the air with the help of three balloons filled with helium. (Photo by Maxim Chernavsky/Xinhua)

Volunteers assemble a bridge made of cardboard and duct tape in Ostankino park in Moscow, Russia, on Aug. 1, 2019. A 18-meter-long flying bridge made of cardboard and duct tape was assembled and installed in Ostankino park of Moscow on Thursday. The bridge was lifted into the air with the help of three balloons filled with helium. (Photo by Maxim Chernavsky/Xinhua)

Volunteers transport a bridge made of cardboard and duct tape in Ostankino park in Moscow, Russia, on Aug. 1, 2019. A 18-meter-long flying bridge made of cardboard and duct tape was assembled and installed in Ostankino park of Moscow on Thursday. The bridge was lifted into the air with the help of three balloons filled with helium. (Photo by Maxim Chernavsky/Xinhua)

Artist Olivier Grossetete (C) works on a bridge made of cardboard and duct tape in Ostankino park in Moscow, Russia, on Aug. 1, 2019. A 18-meter-long flying bridge made of cardboard and duct tape was assembled and installed in Ostankino park of Moscow on Thursday. The bridge was lifted into the air with the help of three balloons filled with helium. (Photo by Maxim Chernavsky/Xinhua)

Volunteers lift up a bridge made of cardboard and duct tape in Ostankino park in Moscow, Russia, on Aug. 1, 2019. A 18-meter-long flying bridge made of cardboard and duct tape was assembled and installed in Ostankino park of Moscow on Thursday. The bridge was lifted into the air with the help of three balloons filled with helium. (Photo by Maxim Chernavsky/Xinhua)

A visitor takes photos of a flying bridge made of cardboard and duct tape in Ostankino park in Moscow, Russia, on Aug. 1, 2019. A 18-meter-long flying bridge made of cardboard and duct tape was assembled and installed in Ostankino park of Moscow on Thursday. The bridge was lifted into the air with the help of three balloons filled with helium. (Photo by Maxim Chernavsky/Xinhua)

A flying bridge made of cardboard and duct tape is seen in Ostankino park in Moscow, Russia, on Aug. 1, 2019. A 18-meter-long flying bridge made of cardboard and duct tape was assembled and installed in Ostankino park of Moscow on Thursday. The bridge was lifted into the air with the help of three balloons filled with helium. (Photo by Maxim Chernavsky/Xinhua)