Athletes vie for the ball during the Mud Olympics in Brunsbuettel, Germany, 30 July 2016. Since 2004, amateur athletes have been competing in various events at the mouth of the Elbe river on the North Sea. The proceeds are traditionally donated to the Schleswig-Holstein Cancer Society. (Photo by Daniel Bockwoldt/EPA)

Martin Weitzendoerfer, diver of Frankfurt's firefighter rescue brigade, leaves a frozen lake during a rescue exercise in Frankfurt, Germany, January 24, 2017. (Photo by Kai Pfaffenbach/Reuters)

Participants of the so called “Victorian Picnic” walk in fancy costumes during the Wave Gothic Festival (WGT) in Leipzig, Germany, Friday, June 2, 2017. Approximately 20,000 goths and other dark subculture fans such as cybergoths, metalheads, steampunks, neo- Victorians, dark romantics, dark electro, industrial, medieval and fetish fans are expected to attend the world' s largest gothic and “dark” culture festival until June 5, 2017. (Photo by Tobias Schwarz/AFP Photo)

Tree trunks are seen in a forest on November 8, 2011 near Landau an der Isar, Germany. The German government is conducting a nationwide project to estimate the number, variety and geographic distribution of trees and forests in Germany, as well as their condition and health. Approximately a third of Germany is covered in woodlands, and though that territory has actually expanded since 1989, some analysts fear demand for wood will outstrip supply in coming years due to national growth in industry and bio-energy needs. (Photo by Johannes Simon/Getty Images)

An interior of a car damaged by the floods is pictured in the town of Braunsbach, Germany, May 30, 2016. The flood tore through Braunsbach, crushing cars, ripping corners of houses and flooding homes during a storm that hit southwestern Germany. Miraculously no one in Braunsbach was killed, though three people died as a result of the storm in other parts of the country. (Photo by Kai Pfaffenbach/Reuters)

A participant competes in the “Nostalgic Ski Race” in the western town of Neuastenberg February 8, 2015. The “Nostalgic Ski Race” is held every two years with about 40 participants and is organized by the ski club of Neuastenberg, a town which was founded in 1713. The conditions for the participation in the race are vintage skis and dresses. (Photo by Ina Fassbender/Reuters)

A knight parades in the street during the traditional carnival parade in Cologne, western Germany, Monday, February 16, 2015. (Photo by Martin Meissner/AP Photo)

A house and garden is illuminated ahead of Christmas in Olching near Munich December 11, 2014. The house is decorated with more than 30,000 lights. Every year hundreds of houses across Germany are decorated by their owners with lights ahead of Christmas. (Photo by Michaela Rehle/Reuters)