Opera singers perform in the pool “AquAria PALAOA” during a rehearsal at the swimming pool Neukoelln on April 27, 2011 in Berlin, Germany. The premiere of the underwater opera AquAria PALAOA is on May 1st. (Photo by Andreas Rentz/Getty Images)

Street fighting in Berlin between Government troops and Spartacists, during the Spartacist uprising which followed Germany's defeat in World War I. (Photo by Keystone/Getty Images). 1919

Egyptian President Hosni Mubarak speaks to the media after talks with German Chancellor Angela Merkel at the Chancellery on April 23, 2008 in Berlin, Germany. (Photo by Sean Gallup/Getty Images)

Keith Richards, Mick Jagger, Ron Wood of the Rolling Stones perform during their "14 on Fire" show at Waldbuehne in Berlin, June 10, 2014. REUTERS/Thomas Peter

In the middle of the lobby of the Radisson SAS Hotel in Berlin stands a AquaDom standing 25 meters tall and is the largest cylindrical aquarium ever built. It’s filled with about 900,000 liters of seawater and has 2600 fish of 56 species.

Two of 20 skulls to be taken possession of by a delegation from Namibia stand on display at a ceremony at Charite hospital on September 30, 2011 in Berlin, Germany. The skulls are from Herero and Nama tribespeople taken by German colonial forces between 1904 and 1908, when the Germans violently suppressed an uprising in what was then German Southwest Africa, which is today's Namibia, and in the process killed tens of thousand of Herero and Nama. German scientists at the time took the skulls back to Berlin to demonstrate the racial superiority of Europeans over black Africans. Many Namibians demand a formal apology from the German government. (Photo by Sean Gallup/Getty Images)

A red fox sits in front of a Eurofighter Typhoon combat jet on the grounds of the 2014 ILA Berlin Air Show, in Selchow near Schoenefeld, Germany, Thursday, May 15, 2014. The International Aviation and Aerospace Exhibition ILA will take place from May 20 until May 25, 2014. (Photo by Patrick Pleul/AP Photo/DPA)

People dressed in underwear run into a store to pick free clothes during a promotional event starting the summer sale at an outlet of the Desigual clothing retailer in Berlin, June 20, 2014. Desigual treated the first 100 customers with a free outfit if they stripped down to their underwear for the first day of the outlet's summer sale. (Photo by Thomas Peter/Reuters)