A Middle East looking guy who spoke German and English approached me and my friend. This was at the side door of the Domo near the W.C. He cornered us and informed us he was a local police and there was an ongoing operation in the area because they were looking for 4 men and a woman who were carrying fake US dollars. He showed a police ID. He insisted on searching our wallets and upon checking that there were no fake US dollars pretended to check the Euro we were carrying. He returned back the money. When he left I immediately checked the money he touched and half of the money was gone. We knew he was a fake but at that time we were 2 women and were scared he might have a knife or some colleagues lurking behind. There were no people yet in the side entrance at that time. I believe he works with a syndicate. BE CAREFUL IN MAINZ!