The mayor of Munich tapped the first keg to kick off the 178th traditional German folk festival Oktoberfest last Saturday. More than six million guests from around the world are expected to descend on the beer tents of Munich to celebrate Oktoberfest which runs until Oct. 3.Last year's visitors consumed some 7.1 million 2-pint (1-liter) mugs of beer. German authorities have increased the security around the fairgrounds this year, although they say no concrete threat exists. A waitress serves ten full large mugs of Spaten beer at the opening of the Oktoberfest beer festival in Munich on Saturday, Sept. 17, 2011. The 178th edition of the world's biggest beer festival, which is expected to attract around six million visitors, runs until October 3. Young people lift up their beer steins after the official opening of the famous Bavarian "Oktoberfest" beer festival in a beer tent in Munich, southern Germany, on Saturday, Sept.17, 2011. A young woman poses with a beer mug in the Hofbraeuhaus-tent after the opening of the famous Bavarian "Oktoberfest" beer festival in a beer tent in Munich, southern Germany, on Saturday, Sept.17, 2011.