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)

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.

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

A Puffin returns to it's nest with a beak full of sand eels on June 25, 2011 on Inner Farne, England. The Farne Islands, which are run by the National Trust, are situated two to three miles off the Northumberland coastline. The archipeligo of 16-28 separate islands (depending on the tide) make the summer home to approximately 100,000 pairs of breeding seabirds including around 36,000 Puffins, 32,000 Guillemots and 2,000 pairs of Arctic Terns. The species of birds which nest in internationally important numbers include Shag, Sandwich Tern and Arctic Tern. The coastline around The Farnes are also the breeding ground to one of Europe's largest Grey Seal colonies with around 4,000 adults giving birth to 1500 pups every year. (Photo by Dan Kitwood/Getty Images)

A 10-year-old pet goldfish named George undergoes veterinarian Tristan Rich's scalpel to remove a life-threatening head tumor in this handout picture taken September 11, 2014 and provided to Reuters by the Lort Smith Animal Hospital in Melbourne, Australia. In a 45-minute long procedure described by Rich as “fiddly”, the fish was sedated by water laced with anaesthetic, the tumour removed and the wound sealed with tissue glue followed by antibiotics and painkillers. (Photo by Reuters/Lort Smith Animal Hospital)

Raising a flag over the Reichstag is a historic World War II photograph taken during the Battle of Berlin on 2 May 1945, by Yevgeny Khaldei.