A Mariachi group performs in honor of a stone which bears an impression that locals refer to as "Devil face", as a shrine frequented by indigenous witch doctors was removed to expand a main highway between La Paz and El Alto, Bolivia, August 24, 2016.REUTERS/David Mercado - RTX2MY0N

Aviator Frantisek Hadrava pilots Vampira, an ultralight plane based on the U.S.-design of light planes called Mini-Max, near the village of Zdikov, Czech Republic, August 23, 2016. Picture taken August 23, 2016. REUTERS/David W Cerny - RTX2MVHJ

Participants hold smoke flares as they slide down along a chute to cross a pool of water and foam during the "Letniy Gornoluzhnik" (Summer mountain puddle rider) festival at the Bobroviy Log Fun Park near the Siberian city of Krasnoyarsk, Russia, August 21, 2016. REUTERS/Ilya Naymushin TPX IMAGES OF THE DAY - RTX2MEHD

People swim during the annual public Lake Zurich crossing swimming event over a distance of 1,500 metres (4,921 ft) in Zurich, Switzerland, August 24, 2016. REUTERS/Arnd Wiegmann TPX IMAGES OF THE DAY - RTX2MV93